I got cheap plastic poker chips (white) and drew exclamation marks on both sides with permanent marker. I'd love to use special dice or cool Campaign Coins tokens, but my brain is like a steel sieve and I'll forget I handed them out; at least with the plastic poker chips they're easy and cheap to replace.
My DM rule for rewarding them bends to the circumstances.
For new players at their first game, I hand out an inspiration point at the beginning of the session. Then, I try to make it a point to reward one for any player roleplaying well; in desperation, if it's near the middle of the first module and I haven't rewarded any additional ones, I'll give it just for doing noteworthy stuff that's in accordance with your alignment. That's to show the players how to get more.
From then on, as the players play, I become more thrifty with my inspiration tokens. They're supposed to be a roleplaying reward, after all, not a prize just for showing up. I reward them for roleplaying a Flaw or a Bond, or for really good roleplaying moments at the table. I take cues from one of my DMs who's also a Fate GM -- you use them to encourage players to opt for decisions that enhance the story, as opposed to easy choices or tactical decisions.
To illustrate, one my PCs in the Hoard of the Dragon Queen had Bog Luck on his hit list. So, he decided he was going to sneak into Bog Luck's quarters and kill him. That would have been the smart and efficient way to do it. But he's a paladin and lawful neutral -- I offered him an Inspiration Token to sneak into the room and challenge Bog Luck to a fight (to be fought under silence) instead, and he took the bait. The challenge had the same end result (Bog Luck is still just as dead) but it took much longer, and resulted in discovery by the night watch (at least partially as a result of the silence spell itself). As a result, the Roadhouse is now alerted to something going on, and it's turned into a much more interesting scenario!