Hi, I am finishing up my basement and I'm planning to put and air return on three rooms that ived built on my basement, will it be okay if I just tap right on my air return duct and put a grill on it just like some people said or do I need to hook up a connnection from my air return duct going to my wall down to the floor? Because all I know is that air return should be near the floor, as in cold air sinks, warm air rise,
Thanks.

Any return you can get will help. You have to remove the cool air from the room before it can be heated. High or low return should work.

Thanks a lot, but one more question, since you said " high or low should work"... will it be okay if I just tap onto the duct itselt before covering it with a drywall and put a grill on it? Tnx

Yep, that will work just fine.

A lot of the newer homes use the drtwall cavity as the return. In a basement I'd put the return on the floor.

Thanks a lot guys for all your help