I've been playing GW2 again after a while away and I discovered that there is alot of lag happening. I asked others on the game but then they keep telling to upgrade my computer. I know for sure it's not the framerate. What's a way to find out if the lag is something on my end or the game's end? Is there a way to improve the connection?

Make sure you don't have anything running or downloading in the background that could be using up your internet, Steam downloads, Youtube, Pandora, Netflix, etc.

And I don't know if this applies to Guild Wars because of their super server thingy, but choosing a server that is closest to you will help reduce your latency (like in your time zone)

Things like port forwarding might help too, or changing settings on your router, but in my experience it's typically the game's issue and not yours. I hope it gets better though : (

Having a powerful processor and lots of RAM really helps. Sometimes just a RAM upgrade will speed things up 100% or more, and all of your other things will work faster and more smoothly, too.

A lot of lag is caused by using up your resources, like Robutt said.

More RAM and a faster processor would probably make it so you can play your game and still have other things running.

If you're using Windows, it has a lot of background processes that run whether they're needed or not, but if you don't know what they are or how to identify them, you should not turn any off, because you can mess up your whole login session that way, and could cause semi-permanent problems that you'd have trouble fixing.

Adding RAM is probably the least expensive way to fix the lag.