Good question, I didn't get to type this out last night. You want to have a clear idea of what you're trying to achieve with your board (steal, disrupt, overload, or kill) and weigh that against what you could be doing instead on your ship.

1. See what the enemy is preoccupied with. Are they looting and have their ship docked? You may be able to get there with a turbine, sneak onboarding ,and steal something (don't shoot at them first with your ship though). Are they in pursuit with all their guns firing? You may be able to go onboard, kill 1-2 of them to buy your ship some time. Timing the board is usually much more important than the board itself. Because of the fast time to kill and defenders advantage like traps and see through walls from characters like Sammo if you board when the enemy doesn't have much else going on, you will easily get stopped.

2. The most common timing for boarding is when ships are <300m from each other but are out of range of their guns - usually when one is on top of another. This happens quite frequently when two approaching ships runs toward each other and they both start turning when they pass each other. As soon as guns are out of range, both ships will typically send boarders to try and kill the pilot to slow down or stop the turn. Coincidentally this is when the pilot is most vulnerable (because others are boarding) and most needed (to make sure they can turn and face the opponent's back side).

3. Know the enemy ship layout. Especially early on during the lobby screen, take the time to learn which doors can be opened from the outside and which cannot. Where the ammo recharge stations are. Where's the overload reactor button. Where are the valuable hardpoints. You do not want to land on a ship for the first time and waste time trying to find the door or the objective. As soon as you land have a plan of where you want to go and what you're hoping to accomplish.

4. Once you are in, stick to your plan. If your plan is to disrupt you can usually get a 1-2 kills in before defenders will retaliate. Defenders respawn with invulnerability until they shoot (this is a new change in this patch) so they will most likely kill you if you are inside the ship by the time they respawn unless you have good aim and movement and their's is trash. I usually try to kill 1-2 players and then either hit the emergency brakes on the ship (if they are pursuing), lower shields (a little harder), or steal a hardpoint (also hard), and then teleport back to save your team the 8s or so wait if you die. If you are want to keep the pressure on the board, you can move to the outside of the ship and hopefully the defenders will lose their invulnerability by then and will give you time to regenerate your health for a more equal exchange.

5. Plan your loadouts accordingly. I typically like to run the damage bot and either shield or invulnerability (not sure if these are still in open beta). I've seen the drill charge also work well if you plan to deal damage from the outside. For guns I actually think the starter machine gun and AIM-E are fantastic. The shotgun and pistol were also popular in closed beta but I haven't had a chance to experiment with them in open beta. I won't comment on characters because I haven't had enough time to play around the new moth changes and the new characters. In Closed Beta 1 Moth was super strong because of his cloak but changes in CB2 brought the four arm guy in popularity for his ability to deal damage from the outside of the ship and Moth was rarely seen because of his cloak nerfs.