User blog comment:Beta917/Skeletron Prime/@comment-4674838-20120710222401

Emphasize survivability over damage:
 * 1) Boost your armor rating up as high as possible. Full adamantite armor with melee helm. Ironskin potions are a must. Accessories with +def bonuses. You should be able to get at least 60 or 70 defense.
 * 2) Get more healing. Heart Statues are amazing. Also, put your Nurse nearby but not so close that she gets hurt. When you take too much damage and are on potion cooldown, use the Magic Mirror to teleport to the Nurse, heal yourself, and get back to the battlefield fast before the boss kills the Nurse.
 * 3) (Obviously) Summon the boss immediately at nightfall so you have maximum time to beat him before dawn.
 * 4) (Obviously) Don't fight near other hazards: lava, Wyverns, etc.
 * 5) (Obviously) Use a decent ranged weapon. Your Megashark with enough ammo is an excellent choice.

^This is a good solo strategy. With friends all doing that, it should be even easier. Though server lag might make teleporting to the Nurse a bit wonky.