YOHOBOJZ'S GUIDE FOR NOOBS!
For twisted treeline my easy to play build for shaco is:
ignite - of course because this ability is awesome for reasons already stated by the original poster.
exhaust - useful if u need to get "just a little bit closer" as shaco says, in order to get the kill.
max archmages savvy, one point in cripple, max sorcery, get embers, and then climb all the way up until you get havoc.
and then i put some in utility like perseverance, one in good hands, max expanded mind, get greed, etc.
Max shiv first for the damage and i get one point early in decieve so i can use it to get in range for shiv.
My build is a little different because it focuses around more ability power and more magic penetration so that your shivs do crazy damage, not around decieve like the original poster's.
1. Tome of Knowledge plus mana or health pot --> mejai's soulstealer. However this may not be useful to some people since they might not be able to get early kills, so turn the tome into a fiendish codex instead.
2. Sorc Boots (or fiendish codex if u didnt get it first item) if u got mejais this goes to 3. and ill just start 3. as 3/4.
3/4. Void staff - awesome ap for the cost plus 40% MAGIC PENETRATION FTW!
4/5. Kage's lucky pick --> Deathfire Grasp. This item is awesome for mana regen, cooldown reduction (to spam shivs) ability power, and, finally, it has an ability that really hurts before your shivs.
5/6. Zhonya's ring - a very important item for ANY ap build imho.
6/7. If you need it at this point then get something that gives ap plus wat u need like say: rylai's crystal scepter for hp (my choice) abyssal scepter for MR (another good choice) etc.
As I said, this guide is very easy to use, this is because it doesn't require much skill. The trick is to hide from the enemy, put down some jack in the boxes and wait for them. When they show up, hit them with a shiv and chase. You can use your ultimate if they have a snare or if you are getting attacked by creeps or another champion. With this guide your ult should actually do amazing damage when it explodes. Keep spamming shivs as they run away and use ignite if you have to. I usually go mejai's soulstealer first because with this strategy I can usually get a lot of kills because imho, this guide helped me a lot more than Carleton's :/ (sorry no hard feelings bro lol).
Your shivs mid game (with mejai's stacks) can do something in the range of 1000 DAMAGE. That's correct, I said 1000 DAMAGE, and your ult bomb should do about 1.5k. I also easily get about 5 second cooldown on shiv, practically spammable 1k damage, a good deal imo.
I showed my friend this guide and he's a noob and he suddenly got really good with shaco (maybe thats because he has a low elo and nobody knows about him when he's not free) but anyways good luck and have fun owning