Let's do a hints & tips thread, current as we can be just prior to Coirnav's launch:
1. Logging in the first day will probably be a hassle. Bobbybick gave a great tip on the official boards: create your character out of Kelethin because it has load balancing [When Agnarr launched I created my monk the first few minutes the server was up and crashed out before seeing Qeynos... took hours to get back in].
2. If saving names and/or starting right away isn't vital... it really is much smoother to not start on day 1 of a new server.
3. group xp has been tweaked on these servers... sure a necro can solo, but even necros will get better xp grouping. If all you do is solo, you may want to play on a non-progression server (unless you are okay with much slower solo progress than has been on live since at least Gates of Discord).
4. Truebox means you shouldn't see mage-armies of 24 characters everywhere. It doesn't mean you won't see boxing. If you want to be a mage army you either need a lot of computers (note... a "computer" can be a very small thing) or should just play on Ragefire/Lockjaw progression servers that don't have truebox.
5. Load balancing means heavy population zones spawn new instances of the zones. This works great for newbie zones when the server is young. This means popular places like Unrest and Lower Guk have numerous instances running while other places are kind of empty. While most on the official boards see load balancing (/pick) as a good thing, it does change things (i.e., people can pick in and take your named spawn, Guk loot will be common as dirt).
6. Agents of change are NPC that spawn raid zone instances. So your family guild doesn't have to compete for open world targets. This is a huge reason for the massive population of the last few progression servers.
7. They are about to patch Zone Experience Modifiers (ZEM) for a bunch of classic zones --the stated intent is to even out the appeal so we aren't all on the same 4 zone leveling railroad.
8. Travel can be a pain on a new server. If you don't want to use your marketplace cash (500 a month with your sub) for potions you may want to choose your class carefully. You get the Origin AA at level 5, which is very handy... but as I found out as a Qeynos monk... origin to Qeynos means needing a lot of ports or spending a lot of time running.
9. Melee is pretty strong on progression servers, but most won't roll their rogues until Kunark itemization. You will see lots of casters early on progression as they (enchanters for sure) are quite strong if you use the full toolkit (especially charm). Many players start with a necro/chanter/mage or even druid to build up coin/gear.
10. If your playtime is limited you are wiser to focus on one character. If you get that character to level cap, and have gear to hand down... then start an alt. Unless you like going hardcore, it is way easier to level alts with handmedowns.
11. Get in a decent guild that wants to play the way you want to play (if there goal is serious raiding and you want to casually level for 3 years --join a different guild).
12. Play nice policy is not enforced. DPS is king. This means you can find drama at sought-after spawns. Bring friends or avoid the drama is my tip.
13. Krono carry across all servers. Many players cash out on one server to restart on new progression. Others use new progression to Krono farm. You can use krono or not. Much gear will be insane prices and then worthless in short order.
14. Some items exist in old prenerf form on progression servers. The dark elf illusion mask is one example. This camp was a drama source early on Phinny and Agnarr but wasn't so bad a few weeks before the drop switched to the nerf version. Circlet of Shadow will be farmed like mad... Agnarr had about 10 of them in /baz when Luclin launched.
15. If you are going to be a raider, stick around for Gates of Discord and Omens of War. With the modern state of progression players are reporting really enjoying this content, while historically many players quit before, during or because of this content. There is a lull come Prophecy of Ro, but the case can be made that most of the TSS and later game is very well done, especially if you like the raiding aspect.