I began serious bluffs in tournaments versus cash game where I'm more nit. I play low stakes. Most of bluffs are usually the c-bet flop. If, however, I get a sense of my opponent being on a draw from the flop, I'll do a 3 barrel (betting all streets from flop to river) increasing my bet amount based on the pot size to make it seems as of I'm already having the "nut". Only works in position for me though. There's some tells online such as the bet amount, the speed of a call or a bet and of course, there's trackers but that doesn't tell me much when it time of bluffs. It's more about following the player you're about to bluff. Knowing his/her type of play.
You just cannot bluff a complete unknown player since you have no way to know of they're calling stations, loose or nit.
Also, there's tempos in tournaments. Beginning, bubble, early itm, mid itm and late (5% left, Final table). You're bluff strategy must adjust at all times.
It won't work everytime, so always think about why you're bluffing and what's the worth and cost.
Poker is a story telling game, you can lie your way through it or tell the truth, but at the end of the day, the goal is to make your opponents believe whatever comes out from your game style.