Bigger is better. Getting the most models possible into a unit is generally the best plan so you can use mob rule. Elite or costly units are an exception.
Shootas are fantastic. If you've got your boyz on foot, shootas are the way to go. If you've got them in trukks, slugga boyz are usually better. Nobs in boyz squads should generally have powerklaws and bosspoles. Some make arguments for the big choppa, but I think it's a waste of time generally. Even shoota boyz can throw enough normal attacks to make even MCs take some wounds, but the klaw lets you reliably kill characters, MCs, marines, tanks, and things like plague marines that the boyz have trouble dragging down on their own. Just make sure the nob is in assist with several boyz or stuck in nice and tight so that even after your opponent removes casualties from the boyz, your nob will get his attacks.
Big Meks should have either a KFF or a SAG. Any big mek not including one of those is a waste.
Warboss with warbike, attack squig, PK, and cybork body is an awesome character. He can seriously wreck some stuff if you're careful.
Other than that, it's mostly up to you to determine how you want to run your force. The 3 basic options are horde, mechanized, or warbiker army. The best setup IMO is horde with fast options. I personally use 2 30-man shoota mobs and a mob of 10 warbikers with my warboss as the skeleton of my force. Stormboyz and nob bikers also work for the fast element, but warbikers are disgustingly shooty and very tough. I support them with lootas and big gunz. A unit of Snikrot-led Kommandos gives me the ability to stop crisis where they arise somewhat or ambush fire support units or tanks from the rear. My army functions sort of like the hammer and anvil, with my shootas constantly coming on, my warbikers hitting flanks hard, and the kommandos tightening the noose.
I don't like mechanized ork armies personally, but others swear by them. Trukks just go down too easily even with ramshackle, 12 orks is not a very effective unit, and the trukk's cost significantly reduces your force size (generally costing 6 boyz per trukk). Also, when you face other quick assault-oriented armies, the trukks don't really do anything for you.
Also, I love the shokk attack gun. It directly adds its points to the hilarity of your games. I call it 'the lulz cannon', and for good reason. You've got to have a sense of humor about it though due to its randomness. At the very least it's the only gun with ap 2 in my army and it's a blast so it can take out terminators and MEQs. Sometimes it slaughters your MEQ and TEQ foes, sometimes it kills the bearer instantly and all nearby (only had that happen on the first round once though). My experiences with it thus far are a bunch of 7s and 9s, some 5s, a 3, a 4, a double 3, a double 6 that scattered to miss the recently deepstriked terminators almost completely (nailed them with a str 7 next turn though that wiped out the rest :victory
, and 3 double 1s. 2 of the double ones were the shot after taking out a unit of thousand sons though.
Orks are great for piles of dice and as the most random race in 40k, plenty of random hilarity. The single best ork tactic? Roll with it, and have fun with the randomness.
