My region lags.

How many times have I heard this line?

You can find out what is causing your lag by employing the Statistics Bar which is available in the Advanced menu/Performance Tools/Statistics Bar.

The main stats you will need to look at is in the Simulator Section - you may have to click down and expand it.

Time Dilation - This should be as close to 1 as possible
Sim FPS should be close to 55

scroll down a bit further

Active Scripts - the more you have running, the less resources you will have of the time frame for all scripts to run.

scroll down a bit further

Total Frame Time - should be around 18ms (in SL it is 22.2ms) but we are different in Opensim.

Script Time - can vary wildly depending on what is happening in your sim at that time.

Spare Time - this shows if you have spare time. The higher number, the better. THIS IS A CRITICAL INDICATOR.
When you have very little or no spare time, it is prudent to look at your scripts and see which ones are being time splice pigs.

I have seen regions that have in excess of over 4K scripts, and the region will run very poorly.
Some regions have this many, but most are dormant and things will be fine.

For example, at region Westfarthing the region is running fine with zero lag. Here are the following stats.
Time Dilation - 1
Sim FPS - 55
Active Scripts - 859
Total Frame Time - 18.18ms
Script Time - between 2.5 and 3.5ms
Spare Time - 17ms (This shows plenty of spare frame time)

Obviously the number of avatars in the region will heavily impact these stats, as we all have attachments with scripts and our avatars draw heavily on region resources/net usage and memory usage by the simulator.

Most grids run multiple regions on the one instance (the instance is another word for simulator).
The simulator (which appears as a little dos box - often called the console) has to share resources/CPU time/RAM amongst the regions that it is running.
It is not unusual for an instance to have up to 8 regions running on it.
However, if one of those regions is using up all it's resources, or it has many errors, it will affect the performance of the other regions in the same instance.
So even though you may have your region away from others, what you do on your region can affect other people's regions.
Try and not to fill it with everything.
Same applies to having a parcel. A lot of parcels have prim limits of up to 5k, which is extremely generous.
However, you shouldn't take that opportunity to fill your parcel to it's capacity, or the region may experience lag (just because you can, doesn't mean you should).
Lets be good neighbours .

Another factor which may impact your lovely region is the mesh you have rezzed.
Say you went out shopping and bought this lovely mesh thingamjig, and it is just brilliant.
However, the grid owner looking at the console and can see mesh errors, usually caused because the mesh item you may have bought in another Grid, was imported in a grid that runs a different physics engine than what is used at your home grid. This problem is endemic in Opensim.
We have two main physics engines - Bullet and UbODE.
Mesh imported in a UbODE environment will have characteristics that make it behave better in that physics environment.
But when used in a Bullet physics enabled environment, MAY cause excessive errors on the region console, and give error conditions,
slowing down processing for that region.

This is just a post to help you have a look at your region, so you can help yourself and determine what needs to be fixed.
Of course, you as the user can't determine if a mesh is bad or not. Only the grid owner/admin looking at the particular region console at the time, can determine that.

I hope you find this information useful.
I am not an expert in opensim by any means, but I have been around a while, and picked up a few bits of information.

Courtesy of Ares Halostar

Solution 1: First try a rebake (CTRL+ALT+R) several times. If that does not help, select Rebake from Advanced>>Character> Rebake Textures.

Solution 2: Check your inventory > Worn Tab to insure your are wearing your usual shape, clothing, etc.

Solution 3: Try wearing different Shape/Skin/Hair/Eyes

HyperGrid Users: It is very important that you make sure your avatar has fully loaded on your home grid before making the hypergrid jump! If you do not wait for your avatar to fully load on your home grid, you may appear as a persistent cloud when you jump to the Neverworld Grid.

Most, if not all, regions in Neverworld Grid run on newer versions of OpenSim utilizing UbODE physics engine. Newer versions of OpenSim and especially in combination with UbODE require all mesh to obey the collada standard commonly used for mesh in OpenSim.

Mesh uploaded on previous versions of OpenSim, which allowed for improper collada - not to standard, often exhibits strange physics behavior, because part of the required data in the mesh is missing. Unfortunately the only option to resolve this is to upload a proper copy of the mesh.

If you are having issues with something you brought from other grids or bought somewhere it is best to contact the original author for a fixed version. Alternatively meshes can be downloaded, if permission allow, and fixed using a 3D modelling program such as blender.

Registration will give you access to additional features not available to guest users such as the following Forums features: definable avatar images, private messaging, emailing of fellow users, usergroup subscription, etc. Outside of the Forums, there are Website features for you to use regarding your in-world persona, such as Friends Online, Money, Groups, etc.

It only takes a few moments to register so it is recommended you do so.

It is possible a web admin has disabled registration to prevent new visitors from signing up.

A web admin could have also banned your IP address or disallowed the username you are attempting to register.

Once you have insured your log-in information is correct, try again. 

Contact a web admin for assistance.

First, check your username and password. If they are correct, then one of two things may have happened. We require new registrations to be activated, either by yourself or by an administrator before you can logon; this information was present during registration. If you were sent an email, follow the instructions. If you did not receive an email, you may have provided an incorrect email address or the email may have been picked up by a spam filer. If you are sure the email address you provided is correct, try contacting a web admin.

If you have forgotten your User Name or Password, do NOT keep trying as you will eventually be banned from the website by our security software. Please use the links for forgotten user name or password.

Don’t panic! While your password cannot be retrieved, it can easily be reset. Visit the login page and click I forgot my password. Follow the instructions and you should be able to log in again shortly.
However, if you are not able to reset your password, contact an administrator.

Neverworld Grid is storing your personal information for a period of up to 6 months since your last visit to our site or the expiration of all your subscriptions (whichever comes last). This information is used to comply with tax laws and provisioning our services to you. We need your explicit consent to store and process this information in accordance with our Privacy Statement. You can revoke your consent at any time, visiting this page. If you do not consent we are unable to provide our services to you and we cannot let you use the members-only (logged in) version of our site.

Neverworld works best with the Firestorm virtual world viewer, which you can download here.

If you already have Firestorm installed but are having problems connecting to Neverworld then you might have a version of Firestorm that only works with Second Life. This is possible because Firestorm comes in two different versions: one for Second Life and one for OpenSim. In order to tell which version you have, start the viewer and select the menu option Help > About Firestorm. The version number should include the words "with OpenSimulator support". If it doesn't then this is the Second Life version of Firestorm, and you need to download the OpenSim version of Firestorm.

Although we recommend using Firestorm, this isn't required. If you prefer, you can use any other OpenSim-compatible viewer.

After downloading Firestorm, you can click this Link: Add Neverworld To Firestorm!

Then simply fill-in your User name and Password and click the Log-In button.

First, check your username and password. 

If you have forgotten your User Name or Password, please use the link for forgotten password.

If you still encounter errors, be sure to check the Grid Status to make sure it is running.

You may contact help using Discord: Neverworld Grid Official Discord Server

Don’t panic! While your password cannot be retrieved, it can easily be reset. Visit the login page and click I forgot my password. Follow the instructions and you should be able to log in again shortly.
However, if you are not able to reset your password, contact an administrator.