You'll need many, many missiles to score significant numbers of hits in a short time - PDTs are very effective on some servers. I'd have to suggest 20-20-20 blocks of Missile-Beam-Explosive, but then I'd say never use anything BUT Missile-Beam. They're also called fast missiles, because they are faster than usual and much longer-ranged. Missile-Pulse is the other one, and it should ALWAYS be used with Explosive effect, because it produces so much damage. It is slow-firing (45 second reload at 100%, I think), packs a massive punch, and travels very slowly over a short range. They can be used, but probably mostly as a short-ranged weapon; otherwise PDTs have too long to shoot them down.
Cannon-Cannon-Punch (or Overdrive or Pierce or Ion or EMP, depending on what you want) is a good solid choice for any warship, a reliable and rapid damage output combined with serious DPM mean it is just an excellent all-rounder weapon. However it will have trouble, given its lowered DPS, with large slabs of advanced armor.
Cannon-Beam is a sniper cannon, long-ranged and hits harder.
Cannon-Damage Pulse is sort of a joke, it's like an antitank rifle almost, very slow-firing but hits pretty hard too.
Cannon-Missile is a shotgun and you should never ever use it for anything except maybe PDTs, unless you're the maniac who has a brawler ship that flies in and scatters heck around the other guy's ship from point-blank.
Other than that, beams have issues that mean they're currently buggy against blocks, but are hitscanning, so they're perfect for anti-shield work (no delay between firing and impacting, means no need to lead targets, guaranteed hits if you have more than ~2 FPS lol). I don't know how much their bugs against armor have been fixed but given current penetration mechanics a beam will give more damage than a cannon round as it goes through blocks as it deals X dmg per tick rather than a logarithmic or something funny like that decreasing function that drops damage like a siv as it goes through blocks.
Missiles are solid for wrecking ships, especially lightly armored ships. Try to trap your missiles so their "bubble damage" effect hits as many blocks around the impact point as possible, so you don't waste it with dmg going into space.
Cannons are just all-round good weapons, especially C-C.
Beams are great for anti-shield work, and if they're fixed will work for blocks too.
Damage Pulse is a joke and you shouldn't use it for anything other than maybe torpedo drones or some such like that .... unless you want a fighter PD system that simply evaporates anything coming near your ship... lol.
And there's my opinion, take note that this is not the only opinion, not necessarily the best opinion, certainly not the only way of doing things, and may be very wrong. Also, if you read this far, good for you. Why are you bothering? Are you seriously going on? Oh cmon, this is pointless and you know it. I'm adding no more content down here, so stop reading here already. Oh, alright, you joker, keep reading - it won't get you anything. I'm serious, here, there's nothing else down here for you.