The Power Selection Plan
Wish you could see how your character will level up into powers and enhancement slots? Well, you can now, thanks to this article, compiling my playing experience and that of CoH veterans with the information available on ParagonWiki's Leveling Chart page.
The Basics of Leveling Up
Up through level 30, you get a new power on every even-numbered level, and 2 enhancement slots on every odd-numbered power (excepting level 1, in which you start out with one power from your primary set and one from your secondary set).
But at level 30, this established rhythm shifts a bit--you start getting 3 enhancement slots at a time instead of 2, and the time between new powers at level-up changes as well.
New Powers Available at These Levels: 30, 32, 35, 38, 41, 44, 47, 49
3 slots available at every other level.
Total number of slots at level 50: 67
Total number of taken powers at level 50: 24
Powers to Choose
In general, it's best to take a balance of powers from your primary and secondary trees.
Attacks: Try to get enough attacks in the beginning so that you have at least one attack recharged and ready to use during battle. (During the first seven levels of my characters' lives, I usually take at least three attacks from my offensive powerset in the beginning, and then use Brawl, Sands of Mu, and my ranged Origin attack as backup.) If you need to take more attacks than this to have more combo-based damage, do so, as comboes are often stronger than individual attacks.
Defenses: Take some of your most potent defense or healing powers as early as you can. Depending on how fragile your character is in a long and extended battle, you might need to take a defensive toggle or two in place of your early attack power grabs. Powers that help you inherently resist certain types of damage are always good to take, as early as you get access to them.
Traveling Powers: With the advent of Ninja Run and Beast Run, it is not as necessary to take travel powers as it used to be. But if you want to take Flight, Super Speed, Teleportation, or Leaping, try to get the earliest power in that power pool before level 14 so you can be ready at any point to take that second (and most important) travel power pick.
A Note about Ancillary/Epic Power Pools
Remember that at level 41, you begin to have access to a small range of Ancillary/Epic Power Pools, special little sets of powers that can further increase your abilities and augment your existing primary and secondary power sets, as well as shore up some weaknesses in your character (Scrappers and Tankers, for instance, can get some minor ranged attacks through some of the Epic Power Pools). Check out the Epic Powers list on ParagonWiki to see the different Epic Power Pools available to each archetype (every archetype has access to a different list of pools).