Also a couple fitting guidelines and why they are guidelines:
Don’t mix guns
This means that you should not mix different gun types or calibers (i.e. don’t put 75mm and 150mm rails on the same ship, or lasers and rails on the same ship), because if you have 1 type of gun, you can group them and they’ll function as 1 unit, which is easier to manage in terms of DPS, range, tracking etc. This also applies to missiles (i.e. don’t mix rockets and light missiles etc).
Don’t mix tank
This means you should not fit your ship with both shield and armour modules. Many new players wonder why because they think “more EHP = better”. No.
Firstly, fit to your ship’s bonuses. If your ship has shield bonuses, it will be easier and more effective to fit a shield tank, vice versa with armour ships. Second, shields increase your signature radius (i.e. making you bigger and easier to hit), armour decreases your velocity, fitting both will make your ship fat and slow, which almos always negates the extra bit of EHP. Third, shields take up medium slots that could be used for utility (propulsion, electronic warfare, computers, capacitor modules etc), armour takes up low slots that could be used for damage amplifier modules. A ship with both shield and armour, in addition to being fat and slow, also puts out crappy DPS.
As someone else said: the best tank is a dead enemy.
Don’t mix guns and missiles
This is fairly obvious why as it presents even worse micromanagement than the first rule.
Don’t undersize your weapons
Fitting a ship suited for medium weapons (i.e. a cruiser) with small weapons will severely cut down on its DPS output. If you can’t use medium weapons, train them first before you take out your medium ship.
Bigger isn’t better
While on paper big guns and missiles look like they can deal huge damage, they are not better. For turreted weapons, big guns (especially long range weapons) have absolutely atrocious tracking. They will almost never be able to hit a small and nimble ship. Big missiles like cruise missiles and torpedoes have damage application problems that make them ineffective at dealing with small ships too.
Don’t overuse fitting modules
Fitting modules are modules that boost your powergrid, capacitor or CPU, while some ships require them to function properly (cap modules are basically essential on larger active shield tanking ships), they take up valuable slots and consume quite a bit of CPU/PG/cap themselves.
Train up fitting skills quickly
Fitting skills will make your ships easier to fit without needing fitting modules. Many of them are relatively easy trains.
Now, remember that I said that these are fitting guidelines, not fitting rules. Many ships and fits break some or all of these guidelines (read: hictors, bait, AC droneboats, battle proc) for good reasons, but as a new player follow the guidelines first and only break them when you know why you need to break them.