What is a polite way to decline an invitation to hang out with someone? [closed]

If someone asks me to do something with them and I don't want to do that activity, how can I tell them "I don't want to hang out with you tonight" and not hurt their feelings?

Normally I say something like, "Not really". I once had a friend say "We are not interested" when we asked them to go to a baseball game. To me that seemed really abrupt and somewhat rude.

What is the best way to say "I don't want to go"?

I'd rather not.
I'm not feeling up for that tonight.
Perhaps another time (if it's the timing and not the activity that is the problem).

How about:

"I'm sorry, but I've already made plans (for tonight)."

That always works, because having the intention to veg out in front of the TV and then go to bed is still a plan...

However, if you want to send the message the first time that you're refusing the offer because you don't like the activity to which you are being invited, there is little you can do to take the edge off the refusal, other than to apologise and give the honest reason as to why you don't want to go.

A couple of milder ways of saying that an activity doesn't interest you include:

"Sorry, ________ isn't really my thing."

"I'm not all that keen on ________. (Though I would love to hang out with you next time you're doing something different)."

The thing about simply saying: "I'm not interested." is that it leaves it ambiguous as to what it is that you're not interested in. (I.e., are you disinterested in what your friends are going out to do? Or are you just not interested in hanging out with them? The latter is what would be considered rude.)

take a rain check
said when politely refusing an offer, with the implication that one may accept it at a later date : I can’t make it tonight, but I’d like to take a rain check.

"Thanks for the invite & keeping me in mind. Would it be okay if I'll call/SMS/email you back when I'd be interested in joining in?"