We all have days where technology is great at not being great. The point of this is to show everyone some things to fix gmod on those bad days.
1. Verify your game for corrupted files.
This is the most common fix for most problems. To do this open your steam library, right click gmod, click properties, go to local files, and click verify integrity of game cache.
2. The antisocial method. Catchy isn't it?
I call it the anti social method because some problems can be fixed just by loading of a single player map and then connecting to the server.
3. The I don't know how to computer method
Most people have lots of viruses on their computers and that can go figure... Cause your computer to not act properly! I made a post outlining some great free anti virus and other garbage removing programs. Usually most Garry's mod issues are software related surprisingly. Here
is the link for how to clean your computer.
My Garry's mod crashes about once a week when I'm on, I believe I have the right to give advice on things to do....