III. Easy fixes (mainly connection)
So, I've explained what lag is and what causes it. Now, it's time to fix it. Typically lag can be easy to fix other times it might cost money, etc (better connection or new hardware). First let's talk about the easy fixes:
Since most of the time lag originates from connection. It's usually caused from simple things such as downloads.
If you're experiencing lag (mostly delay time with connection problems) stop all downloads. By downloads I mean everything. Such as bit torrents, loading videos, updates, streaming music sites, etc. Why videos and streaming music sites, because everytime you go to a site you download things (that's why it's important to be careful which sites you go to), this is because you have to download the information to see the site. So, with videos and music streaming sites (last.fm, pandora, etc) you're downloading video and audio information which uses a lot of bandwidth. So, stop everything.
Now, if the previous didn't help then it could be that your computer is running too many high usage processes and is clogging your CPU. To check to see if that's happening go to your Task Manager, click All User Processes, and look for high usage processes or processes that look strange and like they shouldn't be there. If you're confused about a process and don't know if it's a threat or if it's necessary for your computer to run just Google it.
If that doesn't fix it then you should restart your modem. This makes your connection start fresh again and deletes all useless information that's clogging your bandwidth. To restart your modem:
First, unplug the modem and router (if you have one).
Keep it unplugged for 30 seconds.
Then plug it back and wait till it's fully booted.
re-connect on your computer and boom! It's done.
Unfortunately there are some viruses that eat up your bandwidth and make you lag, which are called Botnets. A Botnet is a virus that infects a host's computer and it turns it into a zombie (i.e. using it to send ping to sites (known as Ddos'ing) or just doing random things with it).
You will not know you're infected until you experience latency lag or if you have a monthly bandwidth internet service and you look at your bill. If you've tried all of the above and nothing has worked, I would think you're infected with your botnet (but still it's unlikely). However, you can never be too sure.. So, I would recommend getting a Anti-Virus and a Anti-Malware program. I would recommend the following:
AVG free Anti-Virus
Now, if that doesn't work then it may be a problem with your internet service. I would contact your ISP (Internet Service Provider) and ask if they can see if there's a problem. Or, it could just be your internet service is very poor quality and I would recommend upgrading it.