This Guide HAS been posted twice, both times by me. I forget to log in when I made the 1st guide so they are near identical.

The goal in your early levels, is to last hit with Siphoning Strike. You want to have about 60 attack build up before taking on a enemy. if you are having a hard time last hitting minions because of a character like ashe or miss fortune, jungle easier monster like the wolves or golems, on YOUR side of the map. Don't get carried away and go into the enemies half of the map. you are asking to die if you try. you will either (a) run into a enemy that is doing what you are or (b) if you are very unlucky, you will get ganked by a couple of people jungling/ambushing.

now your are starting to get stronger, if you have farmed right, you should have your boots and both of your last whispers. now you are ready to put the whoopin on somebody!!! what you need to do is watch the map for allies that are all ready in sight of an enemy, and come up behind the enemy using this skill combo ---> Wither, Spirit Fire, Siphoning Strike.
what this will do is weaken/slow them down, giving you time to use Spirit Fire, lowering their defence so that you can hit them VERY HARD with Siphoning Strike. if that is not good enough, use Exhaust and Ignite on them. and then Siphoning Strike again. YOU will not KILL tanks with this combo, this will only kill characters like Ashe, Tristana, or miss fortune. someone with a lower defence. you should only use this on a tanker if you have 1-2 team mates with you. try to ambush/farm from weak/solo enemys.

now you should have The Black Cleaver. with that, you should be powerful enough to take nearly anyone 1 VS 1 and if you have The Bloodthirster you biggest concern is DO NOT DIE. if you can max out its affects, you will be Life Stealing 33% HP and have 100 attack (60 from the item, 40 from the kills) at this point in the game, you CAN 1 VS 1 anyone (even a tanker) and are especially use-full in team fights. in a team fight, save you Ultimate till you see that the enemies are weak, or you are in trouble. You can activate it to give chase (and maybe a few kills while you are at it) or to run (it will boost your HP, giving you a chance to run without dieing). keep last hitting with Siphoning Strike, The stronger it is, THE BIGGER THE WHOOPIN YOU CAN GIVE YOUR ENEMY.