Hecarim is a great champion once you get the feel and ability to play him. For this guide I will take you through a simple jungle technique to be ganking like pros.

The Item build calls for some serious movement and attack speed.
Start off with Cloth armor and 3-5 health pots
After 1st run through jungle grab mana crystal and boots if you can
Go for another run until you have enough for boots of mobility or you get lvl 6
Then start helping your teammates with ganks will still jungling.
then get 1-2 zeals by mid game
Work on get both Phantom dancers before late game.
Mid-late game Grab and Armor piece that will suit the situation
Do not I repeat DO NOT!! Get trinity Force if you're following this build.

Skill sequence if Important:
when going for the gank you want to use your charge into them toward your turret.
Then spamming Rampage while you use your Spirit of the dead to finish the kill.
Important Using Onslaught of shadows has to be your call and a split second decision can turn a kill to a death.
When using it to engage: Make sure your hidden before using and you want to land directly between them and there escape so it will fear them further away giving you time to kill.
When using to chase down: Just as before make sure you land between them and the escape route.
When using to Escape: From a being cornered in and flash wont make it across the wall use it to go across and charge out, with this guide they wont catch you unless they can teleport ahead of you. From open area just use to the safest area and run out.
remember if you plan on using it to engage you wont have it to escape if something happens.

Very simple: get a leash at blue and have them hit once and make sure they leave to give you enough xp to get lvl 2. Make sure you use smite around 500 health in case counter stealing. Then go straight to Wolves then use Health pot if less than 40% go to wraiths then double Golem important you might feel the need to use smite cause you might die but just use a health pot and if you've been spamming a Rampage and keeping Spirit up you'll be set and wait in brush just in front of Red use Health pot charge in to red smite around 500. Then up to you to get wolves and wraiths again if you have enough health.

Pros:
Threat when unseen
Very mobile mid - late game
Good in team fights
You can't outrun a horse
Good self Aoe

Cons:
Not useful till level 6
Mana hungry
Easy to be "cocky" and mess up

If your getting crushed cause team fed the enemies. Build armor and Magic resistance first
You want to be a good summoner you have to be able to think on the fly. But you still want to get Phantom dancers at some point preferable 2-3.

Shows Jungle route early build. Tow to think on your feet and has some really good ganks and use of abilities. Not the same item build but the game ended when other team surrendered so never got to late game. 18-1-6 final score
http://www.youtube.com/watch?v=CqpiU4PFuBw&feature=g-hist