Solo top: You have to farm alot for make tons of damage, take ghost and exhaust. the hardest champion against you, are: Udyr,Irelia and yorick. try to kill them as fast as possible before they get feed by the creeps or the kills. i dont play him usually solo top i prefer to jungle
About Jungler:Jungle with hecarim is not easy. at the first times you have to recall often and you need a good pull for the blue golem.try to gank as fast as you get the red buff. at level 4 by taking one point in devastating charge is more easy to gank.

At the start 9% critical chance for jungling seems useless, but in the middle game when you got ghostblade you make many critical damage and trust me, they are really helpfull.Armor Seal are required for jungle of it will be too hard.Cooldown runes are always usefull.For solo top player the runes i suggest are the same.

I take 21 points on damage because i like to kill people alone with crit and to disappear in the shadow. and 8 points on utility for movement speed bonus and buff duration.

Youmuu's ghostblade with Hecarim is the perfect item. because it give attack damage armor penetration and cooldown, and when you activate it, it give you movement speed so it chain perfect with the passive, and you gain atk speed too.Last Guardian angel because in late game is very effective.if you play well the game will end at the trinity force..

Pros:-he is really strong against off-tank and carry,
-You run really fast with ghost, yomuu effect, 3 mov speed boots, mage and carry can't run away
-If you play him as a jungler you can get easy ganks with Lizard and devastating charge.
-You can kill squishy and mage like vayne and karthus really fast and run away safe.
Cons:-You are squishy
-Jungle is really hard and you need few try for afford it.
-If you are against any Champion that slow you like kog'maw,nasus,ashe,etc. they counter your passive which means less damage

At the end the only thing i want to said is:

You have to kill and RUN!

this is my first build, i'm not english but i hope you can understand everything, if you have any suggestion about any champion ask me, dont forget to rate and comment and dont be evil!
i play league of legends since June 2010, i know many tricks and other things
hope you enjoy your game and dont rage!