Wow, nothing quite like jumping in at the deep end
Serama are one of the smallest breeds of chicken in the world, and consequently they have their own problems which may not occur with larger breeds.
Do you know which grade of serama you're getting (they come in A, B and C, and any reputable breeder will be able to tell you which grade they are/or will be) Grade A are the smallest, with fully grown adults being about the same size as a regular coke can. Grade C are larger, up to 550g I think (Serama aren't my breed, so I'm not too sure).
As with many species in which size is a factor (either dwarf or giant - chickens, dogs horses) there are plenty of unscrupulous breeders out there, breeding for size alone and not for conformation or health.
OK, I'll get off my soap box now, lol!
Right, with baby serama, you need to know they are TINY! Consequently they need more care and attention than other chicks. They are also very fragile, consequently they need more protection from extremes in heat and cold, draughts etc.
Even if you're getting 4 week old chicks, they will need to be kept in a suitable brooder with a heat source (area under the lamp to be about 25-28*C for 4 week old chicks), chick crumbs and a source of water (a quail drinker would be ideal). They will also need suitable bedding, and as they are so small, you may need to look for something which is finer (but not dusty) than shavings used for horses.
I believe Serama tend to be early crowers, so you can expect crowing from approximately 10 weeks old. Now just because serama are small doesn't mean that they are quiet! I had a sabelpoot cockerel (another true bantam, about the size of a large pigeon), and you could hear him half a mile away! Also, because they are small, the crow tends to be high and piercing.
As they grow to adult hood and looking towards winter, they don't do so well in the cold, and I know many breeders actually keep them in heated greenhouses over winter.
You will also have to be more vigilant about visiting cats, and birds of prey from over head, because the size of the serama will make them quite easy to take by predators.
Now, I'm not trying to put you off completely! I love my 'poots, but they do have to be managed in a different way than my LF birds. I hope I don't come across as "ooh you mustn't do this" because it is not how I intend it, I just want to clue you up as to some of the issues you might face with choosing such a small breed for your first one
Good luck, and if you have any more questions, then post away