Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
Pre-game - Summoner Spells, Masteries and Runes.
First things first, this guide is purely my opinion of ONE of the ways which Shaco can be played, whether or not you agree I KNOW it works for me and I have the wins and kills to prove it; even the people I play with have said how much it works and how much they like it. When I first started playing Shaco I used many other guides and they just didn't seem to fit to my play-style, so after attempting many different builds I came up with this one; a lot of "trial and error". This guide might not suit you personally but it doesn't mean it is a **** way to build/play Shaco; because it works for me. In my opinion the most important thing is to have a build which suits your play-style and that can only be found by you and you only, this guide is here to help you find the build which suits you the most.
I mostly play Twisted Treeline (3v3). So this guide has been put together to fit my play-style on the 3v3 map it could work on 5v5 but I haven't tested this.
Lets start with Summoner spells.
I chose Exhaust because it is extremely useful to get kills; at least in early game. Exhaust itself slows the enemy and weakens their damage output, this added with the point in Cripple (Offensive mastery) reduces their armor which makes your attacks deal more, and slows them for longer.
I took flash because added with Deceive (Q) this makes you extremely unpredictable. For example, deceive in and attack them once, then use E on them, flash forward and put down W and then auto attack them more. Obviously this is just my opinion and for me this works extremely well, this matches my play-style.
Crit chance, Cripple, Cooldown Reduction, Attack speed, Armor Pen, Minion Damage, Attack Damage, Crit Damage and Increased Damage. Most of these are needed and some are just there because I needed them to progress to the next Tier. I don't believe cooldown reduction is that necessary for Shaco, I just don't find it that useful which is why I only put one point in it. Minion Damage is there because I could either put 2 more points in cooldown reduction or Minion Damage and seeing as I don't like cooldown reduction I put them in Minion Damage which can be quite useful when last hitting creeps and jungling. The rest I think are self-explanatory.
Increased health and and mana regeneration, decreased death time, increased buff time, and the most important one %5 increased exp. Shaco is all about having an advantage over your enemies this added with everything else will give you the advantage you need.
For Marks I have Armor Pen runes because I am playing an Attack Damage Shaco and in my opinion these are the best runes for marks.
For Seals I have attack damage.
For Glyphs I used attack damage. This added to the attack damage runes in Seals should give you a decent amount for the start of the game. Add these to the Armor Pen and this will be great.
For Quints I use Armor Pen again, just to get that bit more Armor Pen so I can focus on Wriggle's Lantern early game and still have amazing damage.