A million dollar question. This is completely MY opinion: You get aid depending on you being present at the right place at the right time. The funding scene was pretty bad when I came here, before that almost every CE guy had full aid, but then word spread around and there were simply too many people coming in. I don’t know what the scene would be in the near future.
The best way to get an assistantship would be to do your research about the professors you are interested in working with – get an idea about the kind of work they do, their profile, how many students work for them, and once you think your interests/profile match those of the professor just email the professor and set up a meeting and take it from there. Avoid spamming professors with emails – This is a sentiment echoed by many professors who say many students email them asking for jobs. Seriously, how can they give you jobs just like that? Think about it, and find out the best way to meet a professor.
If this sounds like a lot of work, just wait till the semester gets over and ask your seniors who used to work for professors to give a recommendation for you after they leave. This may not work as the professor might not have enough money for another semester, or he may have a different student in mind, or your friend might not have done a good job at all for the professor to believe him!