this ship has heat issues, so you shouldn't use more than 1 burst or beam, you can have two pulse tho, but you can forget about the heavy weapons like plasma accelerator or railgun
one thing to remember is that Multi-canon are almost mandatory for the courier, they use the full potential of the medium hardpoint and doesn't consume much power from the powerplant or energy from distributor, are reliable (very easy to use), very effective against hull/sub-system and ok against shield, and cheap on top of all that, and if you use them at optimal times they will last far longer than most people think
knowing that, i can think of only few builds that will work in all situation:
1: Pulse, Pulse, Multi-canon
standard, effective, you can do some burst damage with it (shooting all 3) if need be, but you better focus on lasers against shield and use the multicanon either to burn energy (with the pulses) if you have to much or shoot only the Multi-canon to regenerate energy, good thing is that even after using all the bullets you will still have your main source of damage
2: Burst, Multi-canon, Multi-canon
the opposite of the build 1, less damage vs shield, more damage vs hull, about the same damage overhaul if you use all the weapons at the same time, but more dependent on bullets, use this one only if you're not the bullet spoiler type (the ones that watched to many movies of war from the 80's), and when you are out of bullets you should seriously consider to go away
3: Beam, Multi-canon, Multi-canon
almost the same as build 2, some people prefer beams over Burst, i'm one of them, these babies do a scary sound when you hit the hull (like a the dentist

)
triple pulse use to much energy, two beams/burst use also to much energy and to much heat etc... i cannot think of any other build that would be as balanced, effective and reliable as theses ones
Edit: i don't wanna hear anything about Cannon, since the nerf in first beta not only the damage is not enough, but the worst is the velocity of the bullet which is VERY SLOW, don't expect to touch small targets, expect to even miss big targets often, not balanced, not reliable (except for an ASP or a FdL)