I just moved into a new townhome and have noticed that one switch controls 3 outlets, a light fixture inside and 1 outside AND a hallway light. The lights have their own switches but will only work if this switch controlling all of those things is switched on. How do I go about fixing it?
That sounds like your standard basic electrical bodge job, where it once worked, and then some homeowner or handyman got in there and mucked it up good-n-plenty. God knows what else could be wrong in there. Or what else that menace has done!
I gather all this sparky stuff is new to you. You may be better off bringing in a pro to correct that blunder and search for other flaws. They have a fair chance of correcting a dangerous situation.
If you want to take it on yourself, good, but take your time (you don't want to become that menace). Learning electrical is a wide mountain (but not a steep one). I'd hit the library and look at electrical books (adult nonfiction, section 621.3192) and browse a few and find one that speaks your language. Then indulge in reading most of it. That'll establish well-rounded knowledge on the subject, something Google is awful at... and then we or Google can fill in the gaps.