Mind you, I'm great at conversing with small groups or just another person. However my sticking point seems to be in group conversations, since I usually don't like watching television or spending a lot of time on the computer (I'm lost when they talk about sport teams, internet fads, television shows) as soon as a topic like this arises I'm stuck there awkwardly sitting without anything interesting to say.

This is been a huge factor in social events and when me and my usual group of friends hang out. At times I find that I'm not really saying anything...and end up playing it off as tiredness.

I know I should try to change the subject, but I don't really know how to approach it. Any advice for this?

i have this problem sometimes but i dont see it like a problem
just dont EJECT from the situation unless you become really bored with them

when this happens to me i search for my own fun thing to do[talk with someone new, go out of the coffee shop on air,watch a TV if there is one in there...something]
and the rest are welcome to join if they think that it is fun

I covered this in previous posts, but in case you haven't heard this before, I'm happy to go over it again.

We all hate to be ignored or "feel invisible." As an introvert, I would usually be quiet in the beginning and start to open up later on. But then they would ignore me. I struggled for years trying to figure this out. Then...I finally got it.

You MUST start talking to your group RIGHT AWAY. It doesn't matter what you talk about. Even if you just ask how they're doing and fluff talk until they warm up to you, that's fine. You might ask WHY this is. I'm here to tell you that you never leave high school. People of all ages are still clique-y. If you don't start talking to your group right away, the others will pair-off with their mutual interests and conversations and FREEZE YOU OUT. Trying to talk to them later will be an exercise in futility.

The 3-second rule isn't just important for picking up women. It's a powerful tool in all social interactions. You walk into a meeting room at work, start talking to the person seated closest to you. You walk into a party, start chatting with the first person you see. Do NOT procrastinate. It will bite you in the a*s like starting that 10-page paper the night before it's due.

If for some reason, you just don't click with a group despite your best efforts, then eject and move to another group.