1. Mixing weapon types. Ill admit even when I first started out this was something I did. Mixing different types like tetryon and antiproton for example. Some do this because its cheaper, others because they think they cn take advantage of each proc :ie shield stripping, or knocking out subsystems etc. However the problem is since Tactical consoles are limited especially if your not playing an escort. One tactical console can add 30% or more to the damage output of weapons. So by stacking 3+ consoles that all increase one damage type will yield a far greater result then for example one for disruptor and 2 for phaser. The second reason is if you have 5 energy weapons of the same type and one torpedo, then all 5 of those will get boosted by each tactical console. Instead of one tactical console boosting 2 and one boosting 3. Which effectively removes one already limited tactical console. This leads to point #2
2. Tactical consoles for energy weapons of the same type only. General nothing except tactical consoles that increase damage for energy weapons should ever be in your tactical slots. For example antiproton mag regulator x3 . Not Anti proton mag, prefire chamber, torpedo chamber. Unless your running a dedicated torpedo ship avoid using any tactical consoles that increase torpedo damage. 1 torpedo weapon getting a bonus is not near the amount you get from boosting the other 5 weapons you have.
3. Power lvs. This is a subject that is going to get its own post as well, however just for a basic overview . unless your running a ship thats using aux to bat, or a sci ship for its ability you generally want to keep 100 in your weapons at all times. Keeping your power lvs as high as possible is essential for damage, speed, ability and defense. Pay attention to your power lvs and unless your running a build that need power to aux, 99% of the time you need to have weapon power at max all the time.
4. Small arch weapons on big ships. Simple fact if your not firing at your opponent your not doing damage. Putting cannons on a ship that cant keep a target in that 45 degree arc is like not having them at all. So use weapons you find the most easy to keep locked on to your target.
I will probably add more soon