I have a son the same age, and I can tell you that timeouts are pretty hard at that age. Many don't recommend timeouts until 3, for several reasons - this included.
However, we have managed to get our son (after nine months of effort!) to do time outs fairly effectively.
First off, we try to make sure to not have them in anger or to make them punishments. This might be obvious - but worth stating. Time outs are emotionless, just temporary breaks while you and the child cool off - both of you. As such, one useful thing to do particularly at this age is to yourself take the timeout. Go somewhere away from the child - not so far that she's unsafe of course, but put some barrier between the two of you.
Second, we give our son a book during his time outs. One we choose - and if he's biting, for example, he's getting the "Biting Hurts!" book - but still, a book. Time out is to distract him from his course of misbehavior and reset him to normal - sitting down with a book is good for that.
We put him in a calm and quiet part of the house - on his bed, on the landing of the stairs before the gate, etc. - sit him down with the book, and set a timer, the same one we use for non-time-out things.
If he gets up, and moves more than a reasonable amount, then the time out starts over and we re-place him there. This goes three times. If it happens more than three times, he goes into the high chair for the timeout (a safe highchair, as he/she may well rock it or try to get out - not against a wall for sure). This actually works pretty well, as he's used to being in the high chair in the relatively calm environment of lunch. We also found that usually, that's not needed - simply sitting down with the book is usually enough. We don't even necessarily take away toys, if they're not related to the misbehavior.
Finally, be prepared to have a few (dozen) bad experiences - and then one good one. Praise the good one. It takes time and effort, but it will eventually work - even if it seems like a game for a while. The game may well work, in and of itself - the point, after all, is to get your child to redirect from the misbehavior to something else. So what if that something else is a sit down/stand up game? Be consistent, but don't focus too much on exactly the form of what's happening. If it works to get her to stop misbehaving, then that's a plus.