First off, congratulations on striking the earth!
I still consider myself quite noobish after playing fortress mode on and of for almost two years, so I am by no means an expert (never did any terrifying biomes, never dug beyond 2nd cavern, never saw magma even..), but I feel like I have most basics down more or less. So here goes..
FOOD&DRINKS
As stated above, plump helmets are your friend. They can be eaten raw, most other crops need to be cooked. A notable exception are berries, you will find these outside; just (d)esignate a large rectangle for gathering (p)lants and they will come to you.
For drinks, you will need a still and a brewer. Also, a lot of pots and barrels.
Brewing plants or eating them raw will leave seeds, these will be planted in farm plots by your farmer and harvested automatically. You need to specify what crop to grow in a plot for each season separately!
WORKSHOPS
You really need:
- a still (as mentioned)
- carpenters workshop (beds and bins)
- masons workshop (tables chairs and doors, also blocks if you'r going to build walls and such)
- craftsdwarves workshop (rock pots, don't make wooden barrels unless you have a LOT of wood)
I usually also quickly get
- butcher and tanner (next to each other, don't let the hides go to waste..)
- farmers workshop (but you won't really need it right away unless you want to milk your caravan animals)
- jewelers shop (gems are everywhere, might as well cut them)
- mechanics workshop (mechanisms are needed for traps and connecting bridges to levers)
- fishery (as soon as fisherdwarves show up, ie when the first migrant wave arrives)
For a metal industry you will need a wood burner, smelter and forge. The first two are under furnac(e)s instead of (w)orkshops in the (b)uild menu. I usually wait a bit with these, the starting seven have enough on their hands as it is.
You can set a task to (r)epeat, this is very useful (dare I say mandatory) in stills. Once your fort starts growing, don't hesitate do double up on certain workshops. Masons, crafts and stills are usually the first I do this to.
NOBLES
Getting a bookkeeper fairly quickly is advised, it makes your stocks menu (get there with 'z') very useful. You need a broker to trade. Although any dwarf can trade, only a dwarf that has the appraiser skill can actually see what an item is worth. He will learn this after his first trade, so keeping the same dwarf doing this makes a lot of sense.
A manager can be handy, but isn't necessary as long as your population is low. Both manager and bookkeeper need an office to work, these are created from a chair using 'q')
TRADING
You need a depot to trade. Building a depot (as well as certain other buildings) requires architecture, don't forget to activate this on at least one dwarf. Stone crafts are the easiest trade goods to muster up in your first year.
I usually try to buy up all the wood from caravans, as I never seem to have enough.
Also, get some cloth, some thread and some glass from the first caravan, moody dwarves might ask for this long before you can produce it yourself. (Cloth/thread of all origins! So silk, yarn and plant. These moody dwarves can be very picky.)
The dwarven caravan allows you to request certain goods to be brought the next year. Some things I always ask for are wood (better safe than sorry), lignite and bituminous coal (unless it's available at my fort), Iron ore (again, if it's not available) and certain animals (I like sheep, you should at least get a breeding pair of dogs). In your case, you could also order flux stone.
DEFENSE
This is were I feel most incompetent at, but anyway..
Stick to one entrance and plan on how to defend it. Caravan wagons need a 3-tile wide entrance to your depot and can not cross traps. A drawbridge allows you to close this off, perhaps even from two sides: outside bridge down at all times, once a caravan is in your depot, close the outer and open the inner bridge. You need to connect the bridges to levers for this.
If you are going to use a military, start it up sooner rather than later. Build a barracks from a bed, cabinet, armor stand or weapon rack and, with q, assign it to your squad(s) for training. Put the first barracks close to your entrance, so your military might be near when they are needed. Some enemies sneak up on you and are only revealed when standing next to one of your units. People use dogs on chains/ropes for this, I have grown into the habit of pasturing bunnies in my entrance, but am not sure if they actually spot invaders, since most kobold and goblin thieves tend to run into fisherdwarves long before they reach my doorstep.
Dogs can be trained for war or hunting and assigned to dwarves.
Well, I've got that out of my system, hope it's any help (I see some of it got ninja'd while typing this up, but whatever. I second what Jetman says about beds, also, don't forget a dining room!)
On a final note, don't be sad if this fort doesn't succeed right away. I've learned mostly by building forts and focusing on one problem at a time. So first, a fort where there's enough food and booze. Then, a fort that has proper housing. Then a fort with a metal/clothing industry or a hospital etc.
In my current fort I have a somewhat organised military for the first time and a somewhat functional clothing industry. Soap, glass or powered machinery I haven't even touched.
But I'm having fun, and so will you!