Although certain hybrid champions or spell based AD champions (Riven) will benefit from alternative masteries like Spell Weaving and Blade Weaving, these should get you started on the right path.
Let's check out some common mastery allocations and the unique points you'll want to look out for.
First up, the Marksmen (Markswomen?)
This is probably going to be your ideal marksmen set-up. You'll notice that I opted for the defense tree, which allows you to make up for some of the extra damage you'll be taking from Double-Edged Sword (see below).
You'll also notice that I opted for Feast (+2 hp +1 mana on minion kill) rather than Dangerous Game (5% health on hero kill). The reason for this is that that 5% health from killing a champion will only be helpful in rare situations, while Feast is certain to help your early game sustain.
However, if you're playing a big snowball champion like Vayne, I could see it being helpful once late game hits.
For the defensive tree, if you're playing a champion like Ashe, it might be worth it to drop that point in Oppression instead since you'll almost always have the 3% damage reduction in effect.
Unique Marksmen masteries
Double-Edged Sword is going to be more useful on Ranged than on Melee, simply because Ranged will have greater ability to kite and absorb damage than melee. Although it does increase damage taken on your champion, I'd still recommend taking a point in this for "da-big-plays"
Defense Tree 9th Point Choices
In regards to what to pick for the 9th point in the defense tree, it seems like Juggernaut will be the best of the 3, as it will be useful for the entire game without relevance to any skills you use or plays you make.
Oppression may be useful for a champion like Ashe (who has constant slowing ability), and the +2 armor will be helpful if you decide to trade very early on, but otherwise Juggernaut is your safest bet.
9 Points in Defense
Next let's take a look at AP Masteries. You might notice that in this first scenario, I've opted for a tanky AP build, putting preferring the sustainin/minion killing masteries over sticking points into the % ap or % cooldown masteries. The reason for this is that AP champions will generally have a slightly harder time last hitting, the extra minion damage and sustain will do more for your farm game than a minor cooldown point (which will be likely be maxed out with blue buff + athene's) or ability power.
9 Points in Utility
Some people might think that the utility tree offers a decent bonus, in which case the masteries pictured above might serve you better.
For those of you looking for Nasus or Renekton masteries, this set will likely fit the bill, once again opting for the Feast mastery. Although it's really not a major game-changer, for a mere 2 mastery points, it's got some sick benefits.
Swap around the armor/magic resist masteries to best suit your laning opponent. Armor is always a better bet if you're not sure who you're up against.
Special Defense Tree Skills
This isn't bad if you're up against a champion that you know will probably rush infinity edge, like Caitlyn. However, definitely don't bother getting it if you're up against an AD carry like Ezreal or even Vayne, who will likely rush Blade of the Ruined King, making this a completely wasted talent.
DEFINITELY get Reinforced Armor against Tryndamere though!
Getting a point in Evasive against an AOE heavy comp's not a bad idea either. Just take out the point from Magic resist.
Supports:Since the meta will likely change with the new gold generation in lanes, it's hard to say what the optimal support masteries will be. However, something along these lines will work if the meta remains similar to the way it's been.
It will be more likely that we'll see an extreme influx of more Annie/Fiddlesque supports in the future. Stay tuned for strategy updates!
There's been talk of junglers being phased out with the changing meta...however, for the most part the masteries for junglers will likely be molded to suit their role. For instance, tanky junglers may opt to go more towards the defensive tree path and offensive carry junglers towards the offensive tree.
The only two masteries that will definitely help in the jungle are the Butcher and the Tough Skin masteries, so those are likely going to be your trees of choice (the buff won't be quite so worth it unless you're playing someone that has a rough time without blue.)
Comments? Agree/disagree? Think Utility is the best tree in the world? Post below!
Stay tuned for more posts on single mastery point comparisons + meta changes!