- You don't have to wait until the wheels that set timed mechanisms in motion (in tombs and such) reset naturally if you fucked up and want to try again. The positioning is a bit finicky, but you can totally use the wheel to restart the puzzle manually.
- Starting or finishing a mission brings you to full health.
- Visit the fighting trainer at your villa as soon as he's available. He has a bunch of techniques he can teach you, but the game never really tells you so you can go by most of the game before realizing it.
- Dump all your money into Villa Improvements. Drown in a tidal wave of cash by mid-game.
- Try to wait until you're at your villa to buy armor/weapons due to the discount you get when you renovate the shops.
- A lot of the chests at your villa (which you can see on your mini-map) are unreachable until you renovate some city feature nearby.
- You can't reach the central tower of Venice until a certain story mission.
- You're going to climb every tower in San-Giacomo on your second visit, for quest-related reasons. This is going to be much less of a chore if you haven't climbed each beforehand.
- There is one (1) jump in the game that can only be accomplished by jumping straight up without touching the movement stick. The game never asks you to do this at any other time and if you're like me, you probably didn't realize you even could.
- Running up a wall then jumping left or right allows you to make certain tricky jumps. You'll get stuck about halfway through the game if you don't remember this fairly esoteric ability.
- I know everyone loves exploring, but hold on on doing so at the beginning of the game until you gain your robes and hidden blade for your own sake.
- There are treasure maps for sale at the art stores; only buy them if you're really into completionism because you get no reward for grabbing all of the treasures and if you focus on upgrading your Villa as mentioned above you'll be swimming in cash. If you do want to complete everything, though, buy the maps as early as possible.
- On the other hand, you should be using a feather guide as you go through the game - it's much less painless to clear out districts of feathers as they unlock in comparison to cleaning them up after you've beaten the game. And there are rewards for getting all the feathers!
- Keep a lookout for rooftop edges covered in pigeon droppings (or some other white substance resembling pigeon droppings; usually, there's also a couple of pigeons sitting on it). These pigeon droppings spots indicate that you can do a leap of faith (one of those "survive a 100-meter drop because you land in a haystack" things), which is often a convenient way to get down to street level.
- You can jump into water from any height without being hurt, so it's a useful alternative to hay. Also, watch out for shallow water in Forli.
- The DLC is worth buying, but it only kicks in after you've beaten the game. Don't feel the need to buy it until you've done so.
- The Bonfire of the Vanities DLC is very repetitive. Only buy it if you really want more assassination missions, since it's 10 of them in a row.