I must admit I haven't read the other responses so forgive me if I repeat what have been said, but I did what you're doing, same mod etc and maybe I can share my experience. I hope it helps !
Enclose your building
When you just embark, your very first priority should be to design a hall, be it temporary, to clearly define what is in and what is out. Humans are give or take as strong as dwarves when it comes to fighting, so they will be preys to wildlife very soon in the game. Cut trees, build a place where you can retreat and be safe from wildlife. In the long run, use drawbridges to make it completely hermetic ; but having walls and doors between you and the wild is a must have at the very beggining.
Keep an eye to the timer
This is especially true if you're playing in a young world. There is a lot of werebeasts around, and they have a chance to visit you every month. Having a military early on is a very good idea, if you can position their barracks between you and the wild, the better.
You can make use of chained animals to detect werebeasts early on. As a outdoor fort however, you have no way to absolutely prevent werebeast attacks, and you want to be super prepared for them
Make careful use of renewable ressources
Wood is necessary for everything. From early building blocks to charcoal, which is the basis of human industry, you need it a lot. Make sure to keep an eye on your wood stockpile, keep it stocked up, and diversify your industry when you can. Having leather and rope reed industries is a very good way to generate dorfbucks, especially if you can dye threads and items.
Wood is plentyful at the beggining of the game, but when you advance in years, it becomes precious especially on small embarks. Glass require wood, clay require wood, metal require wood, wood require wood. So make sure you have plenty of it and don't rely on wood consuming industries if you have alternatives. For exemple, make your crafts of cloth, as it is easy to produce. Human traders come in every summer, and have some weapons and bars with them you can use to gear your troops.
A strong military is a must have
As soon as you can, start a militia. Train them like theres no tommorow, and use your ressources to equip them. If you have a leather industry, make shields and early armors with that. Switch to metal when you can reasonably do the transition.
Especially if you don't mine, your military is a raw material industry, you use it to extract goblinite. 20 legendary fighters can defeat 150 goblins without losses.
I'm sure I'm forgetting a lot, but that's the lessons I learnt from my last game
How do people approach housing on a surface fort? I'm building apartment complexes for thematic reasons. Is dorms more common or do you need rooms to help offset the rain penalty?
If you play as humans, don't worry about the rain penalty. Common rooms are enough for all your non nobles. If you can, train your woodcrafters by having them making wood blocks, then have them draw mastecraft beds and furnitures. Your little people will soon forget the rain outside. Also, alcohol. It helps a lot.