Some lessons we've learned from living in the wormhole:
1. Wormhole Class- If your corp contains a large number of noobs (like me), and you are set on going into a wormhole, stick to the C1-C3 variety and only the ones that have an exit to known space. It doesn't matter if it's a high sec, low sec, or null sec static exit, just make sure you have one. We lived in a C4 with a static C4. The problem we commonly faced was 3-4 hours of scanning to find our way out of our wormhole. Our C4 would link to a C4, which may link to a C5, then a C4, then a C3, then a C1, then an exit to known space. THIS IS A SERIOUS PAIN IN THE ASS FOR MANY REASONS. Sure, we mined lots of ore, killed lots of sleepers, etc ,but if we wanted the ISK from those gains, we had to load up some ships, go to high sec and sell our stuff, and then hope we didn't get attacked along the way in other people's wormholes, or have a wormhole collapse on accident and not be able to make it back to the wormhole for days.
2. Mining- Not sure what is truth or myth about how frequently sites respawn, so I'll just describe our own experience. LOTS of money can be made mining "when" there is a Grav site to mine from. We initially were told to not completely mine the site so that it would respawn, but then it disappeared anyways. Then we decided to mine it all the way down, and it's been over a week and no new grav site. All the miners in the corp were initially drooling from the rare ore and the vast amounts of it, are now they are bored out of their skulls watching paint dry in the wormhole with nothing to mine.
3. Sleeper sites- These vary in difficultly, but I learned you can look up the type of site online by googling the site name such as "Frontier Command Post" and they will tell you what types of ships to expect, how many, how much DPS to expect, and recommended fleet size to be effective. General rule of thumb, sleepers can drop extremely valuable loot, and nano-ribbons from salvage are very valuable. Just expect to take lots of damage, expect to get warp scrammed and webbed, neutted, and generally get pounded hard to earn this ISK. C1-C3 sites can be solo'd much easier than the C4-C6 sites.
4. Collapsing wormholes- Either on purpose or on their own, wormholes collapse. Each type of wormhole has a set time and mass until it collapses. You can't change how quickly the clock counts down, but you can collapse a wormhole by putting too much mass through it. Know the mass limit, what the warning messages are for how much more mass it can take, and accept that if you are purposely collapsing a wormhole there is a 50/50 chance you'll get stuck on the wrong side when it collapses. When that does happen you can either scan your way out or self destruct (not recommended if you have a bunch of implants or if your ship is worth a lot of ISK.
5. Death- You will die. Accept it now and plan for it. Bring spare ships and for heaven's sake don't bring all your faction mods into the wormhole, if you do, kiss them goodbye. You will lose ships, accept it now and you won't be as upset when it happens.
6. Stealth- If you can't use a cloaking device, don't move into a wormhole until you can. Even a prototype cloaking device is fine, but if you can't hide, you're dead.
7. Scanner Probes- If you aren't any good at scanning, don't move into the wormhole until you are. I like to use the Sisters of Eve Expanded Probe launcher and sisters of eve probes. They add a little more bonuses to your scanning efforts. Once you've launched your probes, turn on your cloaking device and scan while you're cloaked. If you forget to cloak, you're probably going to get popped.
8. Trust- Although you need to have some level of trust with your corp mates, overall you shouldn't trust anyone. Unless you know them in real life and have the ability to knock on their door for stealing a few billion in loot from your hangar, and even then, I probably wouldn't trust them.
9. Belongings- First off, don't bring what you can't afford to lose to the wormhole, because you probably will lose it. Second, bring enough that you don't have to run back to high sec every time your ship gets blown up. Have a few extra ships on hand, but not so many that you would be broke if the POS got blown up. Leave the Navy issue ships out of the wormhole and all your faction mods out of the wormhole too.
10. NBSI - NOT BLUE SHOOT IT. Period.