More/Team Strategies

Cutesy?

While Orcs might have cutesy alternatives to their main strategies, Humans just have more real options. Orc Raiders can be pests. Human Steam Tanks are end-game, particularly if you can sneak them in using the Archmage's level 6 Teleport ability. Bloodlust and Healing Wards do no good to Tauren if they're sheep. The Orc's only dispel is Purge, which costs a lot of mana (75), affects only one target, and the Shaman probably doesn't have any mana left to cast it after auto-casting Bloodlust on anything that moves.
The Sorceress' Slow spell effectively cancels Bloodlust, but save some mana for Polymorph, particularly when you are outnumbered. Don't waste Polymorph against Night Elves who have Dryads since Abolish Magic is an autocast ability. Against armies with Dryads keep Slow and Inner Fire casting, since the Sorceress and Priest have more mana and regenerates it faster - especially in range of an Archmage with Brilliance Aura. Dryads that are dispelling are also Dryads that aren't attacking. Use the Priest's Dispel Magic on Skeletons, Treants, summoned Wolves and enemy Water Elementals. Alternate between auto-casting Inner Fire and Heal, for maximum effect.

Teamplay changes

Humans are a great teaming race. What separates them from the "good" others is their versatility, the Priest's Dispel Magic and their heroes. Dispel Magic is just utterly abusive. It cancels any kind of effect. Entangle, Bloodlust, Purge, Frenzy, Faerie Fire, Inner Fire and Web all fall before the might of Dispel Magic. Dispel needs to be cast manually by the player but it has area-effect. It nulls and voids the Undead skeleton hordes that appear in massive battles. Just about the only thing Dispel Magic can't do is rid of the world of boy band music.

In team matches, the normal Human start works well. Footmen or Riflemen work fine, accompanying the Archmage (usually) or Mountain King if you're feeling different. Support casters are a must and can be followed up by Knights, Gryphons, or even Tier 1 units. Humans have some very nasty tricks as well, centering on the Archmage's Teleport or Sorceress' Invisibility. Sneaking an army of Steam Tanks into an enemy base is utterly devastating.

A Human Footman / Undead Ghouls rush is very fast and effective. The Archmage's Water Elementals add significant ranged power to it, while the Undead Dread Lord should have Sleep to knock out enemy heroes. If you're going for a hero-killing force, get the Mountain King with Storm Bolt and Undead should have Death Knight with Death Coil. Night Elves with Archers and a Demon Hunter work quite well. Orcs just won't be ready in time.

Of course, later in the game you want to have more support casters than you normally would, and fewer melee units. The exception is a quick assault force of Knights. Their speed and ability to flank a foe are great offensive tools. With their high armor, they survive quite long even against prolonged support caster fire (which, unfairly, does piercing damage vs. the Knight's Heavy armor.)