I use a two-tier system.
1st Tier military dwarves train year-round and are heavily armoured. They make up less than 5% of my fort. They're either Macedwarves armed with Morningstars or Axedwarves armed with Halberds. I like these two because of the wide range of wounds they can inflict.
Helm, Face Mask, Mail Shirt, Breastplate, Gauntlets, Mail Leggings, Low Boots (current world only), Buckler, Weapon, Leather Vest, Leather Cloak, Leather Hood. I use bucklers because they're lighter and, I think, more effective as a weapon. These dwarves can dodge/block most attacks, regardless of the shield size.
2nd Tier military dwarves are, basically, dwarves put in a military squad so they can carry weapons around for self-defense. They normally have a Mail Shirt, Helm, Shield, and Spear. I ALWAYS give them spears because that's the most effective weapon in the hands of a poorly-trained dwarf due to the high penetration. Dwarves that already carry weapons (Miners, Woodcutters, Hunters) aren't placed in a squad.
I put a lot more effort into equipting the 1st Tier dwarves: I'll dig down 40z-levels for marble and level the entire cavern for wood to make charcoal and Steel, but 2nd Tier dwarves get Iron at best, and Bronze Shields if it's avaliable (Bronze is arguably the best blunt material due to the good density and the toughness. Silver is too weak, although it is heavy).
I always embark with 2 Miners, 2 Masons, a Doctor, a Mechanic, and a Stonecrafter. The stonecrafter makes goods year-round to buy out the carvans.
Also, I'm currently playing a Goblin Fortress, and the best combination of weapons/armour seems to be massive shock-squads of lashers that disable the enemy while the well-trained, well-armoured Scimitar squads finish them off. All supported by War Trolls, of course. I added Brass as a weapon material, and it isn't too bad. It's 8th out of all metals in regards to cutting power, and makes better armour than bronze (arena testing).
Finally, when playing as a dwarf, I always try to capture Naked Mole Dogs and train them for war. They're superior to Dogs in a fight.