I usually accept all comers in my forts. The only time it's a problem is usually in the second year, when I have around 20 dwarves and a wave of 20+ will arrive. But even then it's not really a problem, just some of them will have to wait a bit to get a private room. I typically have a dorm set up with a dozen beds or so, which will serve nicely for a few dozen homeless. I tend to go with modular bedrooms that I can quickly designate for digging in groups of 10. So I just designate a set of 10 rooms, and at the same time I add to the job queue:
10 rock doors
10 beds
10 coffers
10 rock cabinets
When the mining is done, the furniture is usually close to done, so I can just put it all in place. Then I designate another 10 rooms and queue up 10 more sets of furniture.
By the end of the second year, my miners and mason are skilled enough that I've gotten caught up and then I keep 10 or so more rooms than I have dwarves. Considering that married couples share a room (and I think their children do too), that means I actually have well over 10 rooms available for new arrivals.
I also use Dwarf Therapist to screen the newcomers. As soon as I get the announcement I re-read the dwarves in DT. It shows the newcomers immediately, unlike the units list in the game. In DT I group by migration wave so I can see the newcomers, and go down the list looking at skills. For skills that I only need/want one of, I just leave it on for the dwarf with the highest skill, which may be the newcomer or may be a current resident.
"So, Urist McMigrant, you're a professional bonecrafter? Well, we've already got a great bonecrafter, so no bonecrafting for you! You get to be a hauler, unless you get drafted. Report to the dining room on level 4 to wait for hauling jobs, it's just below the kitchens. Next!
Ahh, you're an adept cook? You're in luck, we have enough work for 2 cooks here, and we have an expert and a proficient, so you get to replace the proficient. He gets to go into the hauling pool. You can head down to the kitchens on level 3, right below the farms. Next!
An expert miner? We can always use miners! Grab your pick and head down to level 6 and start digging out your new bedroom. Next!
A skilled surgeon and skilled bone setter. Well, we've got a talented surgeon, and a competent bone setter, but it's always good to have extra doctors around in case one is sleeping when we need emergency surgery, so we're happy to have you. Head on down to the hospital, it's on level 5, right above the bedrooms. Next!
A talented leatherworker, eh? Boy, Urist McMason will be happy to see you. He's been moonlighting as a leatherworker since we founded this fort, and he'll be happy to let you take over the job. You'll find him in his mason's shop down on level 8, where you'll also find your leatherworking shop. Confidentially, the soldiers will be happy to see you, too. Urist McMason does his best, but he's only a novice leatherworker and frankly, his cloaks suck. I'd rather have one taken off a dead goblin. But don't tell him that. Next! Holy Armok, how many migrants are in this wave?"