Ok I got this Dirt Devil bagless vacuum from my sister and it worked great for like a week and then it stopped sucking... Should I change the belt or the filter??

Try cleaning the filter, if it still doesn't work, return it, it may be faulty!

empty it and clean or change the filter. Also check the hoses to make certain there isn't a huge clog in it somewhere -- possibly you sucked up something that is stuck.

empty it and clean or change the filter. Also check the hoses to make certain there isn't a huge clog in it somewhere -- possibly you sucked up something that is stuck.