Support skills
Support Skills are those skills which affect how well you can fit/use/fly ships and modules, without being skills directly required to use the modules or enter the ships. Common examples are capacitor-related skills such as Energy Systems Management, and fitting skills such as Advanced Weapons Upgrades.
Since 'good support skills' is a cliché in the Uni and EvE generally, this page attempts to define the skill set and suggest what levels qualify as good in what circumstances. Wish us luck.
Expectations in Various Ship Classes
The heart of the brawl is that a skilled character can double the damage and defense of an unskilled one flying exactly the same ship. And, of course, you can put more and better stuff on the ship besides.
Battleships
T2 guns on battleships can be great, but the training time for T2 turrets is on the order of 70 days, from basic T1 large gun skills. They're currently considered vital only for Amarr battleships, and that's on economic grounds (Meta-4 large lasers ran about 22M isk each, last time I checked.)
Battlecruisers
A battlecruiser is a nice step up from a cruiser in firepower and tank. In fact, it's the first hull you're likely to get into where fitting a tank has real meaning. The cost of the fitted ship is also a lot lower than a battleship (1/3 to 1/4 the price), and you don't have to have large guns trained. Which is to say, you don't need to be overly timid about moving up from a cruiser.
Support skills you'll want to work towards are the ability to fit a T2 armor or shield tank, good enough fitting skills to fit all the turret/launcher slots, and eventually T2 medium weapons. If you have medium gun/missile skills to L4, and can fit a t2 tank, I wouldn't hesitate to step into one of these. You should also be able to handle a full flight of drones (Drones V), since battlecruisers generally have a drone bay -- and you'll want light drones to harass tackling frigates and so on.
This is also the first hull you'll encounter that generally has rigs installed. You can use rigs without having the rigging skills trained, but you'll need someone to install the rigs for you, which is a pain -- so you may want to train rigging skills for whatever you're fitting.
T2 Frigates
Support skills depend on the particular frigate, of course. An extreme example: you can fly a covops ship without putting a covops cloak on it, but you'll be missing the point completely.
T2 Cruisers
In general, at this level you should be able to fully T2 fit your ship. In practice, you'll need Weapons Upgrades 5 and a couple levels of Advanced Weapon Upgrades (AWU), or you'll be very frustrated trying to put guns on. T2 cruisers are small, fast, and powerful, but tend to have limited CPU and/or powergrid, and limited capacitor as well. You'll want your cap skills and fitting skills to be nearly maxed-out before flying one of these.
T3 Cruisers
Fitting Skills
Damage-increasing Skills
Rigging Skills
Overheating
In a sense, the ultimate support skill -- you can use a module beyond its design specs, though eventually burning it out.