I can't think of one technique I use across the board, but there are some general strategies. First, I make sure that there's an agreement about who is responsible for an action or outcome and a clear definition as to what that action or outcome is. That could come in the form of a meeting, or a one-on-one conversation, or a phone call. It's possible to do by email but written communications increase the possibility of misunderstandings in my view.
Second, I try to learn what mode of follow-up works best for a given individual. Some people will accomplish what they agree to without follow-up. Others may respond well to reminder e-mails. Some people respond better to phone calls, texts or in-person meetings. It's all a matter of understanding the people you're working with and how best to hold them accountable.
I think the formula is pretty much what's outlined in the GTD book: define the next action or outcome, decide who is responsible, and if it's not you track that item in a Waiting For list to follow up on regularly. I've found that simply following up with people is surprisingly powerful.