I play Hecarim as a jungler. My build allows him to be a very burst oriented ganker and really shines when he can get around behind the enemy or to their flank later in team fights. I'll break things down in their catagories...

Smite: I jungle.... so Duh...

Heal: feel free to switch this one. I like really use the Heal bait tactic. I also use it for when I tower dive and cut it close to get out, argument being flash is better for that, I say its a team game I like to share the health.

Ghost: over rated for him, already ignores unit collision and has enough speed to chase down or run away from pretty much everyone...

hec is pretty weak for his first 3 levels so you need the tank masteries to jungle. Also my build focuses more on Dmg than on tank gear... just go with it.

your focus is

R > W > E > Q

open with Q then go with the above formula. Reason being your W is a highly underrated source of sustain, WHEN used with someone else. No by himself it isn't amazing but in teamfights and during ganks when 20% of the dmg that your AD carry is doing durring your gank you get as health back... just smile and nod when the other team complains why won't you die.

Next up Q is nice and all but i use it to make sure I have a sheen proc ready for when my devastating charge hits, the sheen proc stacks on top of this and the dmg you can deal is on par with a Poppy devastating blow.

Some tips for using his ult. Most guides say to open with his ult when you charge into a team fight, I disagree. When you see the right moment to attack use your charge to come out of brush either behind your target or at least on their flank. Try to hit them away from where they will want to run. Generally after you hit them they will want to flash away from you, THIS is when you want to use your ult, they flash you chase with ult and leave them feared and easy to run down.

besides that use your Q to set up sheen procs or while some one is running away just try to run in front of them as best as possible and keep hitting Q and auto attack when sheen comes up.

Standard AD jungle runes Armor Pen, and Armor

I'm a Big fan of CDR if you don't like it try something else.

and move speed quints, just keep feeding his innate ability.

Open boots and three pots
Upgrade to swiftness as fast as you can
next item is sheen, this is when you can rally start doing some high dmg on ganks
follow it up by getting a phage for its proc effect as well
finish your triforce when able

after this it depends on your opposing team, if they are packing a lot of AP I build a FoN and then going in to the 2 zeals, then IF, then upgrade to Phantom dancers.

if they are mostly AD just go straight to the zeals

other option that I sometimes use instead of the Bloodthirster is a Gunblade... makes him very strong sustain and and the slow shot is nice.

Ask for some Wolf dmg and a leash on blue
kill order is:
wolfs
blue (pot)
wraiths
golem (pot)
at this point you will be level three and have all your abilities, look for a gank (pot if need be) or (use your heal near a lane that could use the HP as well)
kill wraiths and wolfs one more time and you should have enough to upgrade boots
go kill red then look for ganks again.

In short, he is built as a bursty charger that excels at hunting down squishy champs and escaping from threats.

Please throw up a rating if you try the build, and feel free to leave any comments below.

Happy Hunting!

trying to upload a picture of my match history... as soon as I figure out how to do that that I can show some of my game results with this build and tactics.

Including 8-0-7 and 8-2-11 in ranked games
11-1 and 7-1 all are great KDA ratios