There is a little mystery and a lot of trickery around domains names. There is the decision on what to have, where to buy it from and how to setup and manage it. Here is a short list of some of the basics for the newb domain name purchaser.
1) You can have more than one domain name pointing to your website.
This can be very handy. Lets say you have a business name that doesn't translate well to a domain name and you are sick of repeating it to clients and think you are losing business because of it. You can have a secondary domain which is catchy and easy to remember and your primary domain as the business one. Both domains take the user to the same place.
2) You can have sub domains
This is were things can get tricky and fun. A nice little SEO trick I like to do on larger sites is separate out the sections and put them on subdomains. This is great for security as you can keep them in separate parts of the hosting account or even in separete servers. A typical example is putting a store on a separate domain like shop.yourdomain.com or blog.yourdomain.com
You can also do this to separate out emails into departments. Also you can sneak your way into a domain that may have already be purchaseds, such as; carsales.com is long gone so you buy rsales.com and create ca.rsales.com (beware trademarket).
3) Your domain for email should be short/simple
The number of times people have given me there email and it is firstname.lastname@example.org astounds me. My rule is you should be able to quickly tell someone your email and they should be able to write it down or recall it with easy. If you have to repeat it multple times you are doing it wrong. Theres nothing wrong with having a shorter catchy domain just for your emails. If your developer doesn't know how contact the hosting company or someone like us (cloud.mebsites.com).
4) Cheap domains are expensive
I so often run into this with clients. We will get our own domain because we thing we can save $2-10 dollars and we don't want to get ripped off.
Then they proudly anounce '...yes I only paid $7 for 1 year for it'. Ok great good for you. Well client you should really get more than one year 3-5 should be the minium it does effect your search ranking (minor) and it definitely affects user perception if your site has we are perminant and stable all over it but you only spent 12 months of $$ on your domain. Not good. So no problem they go back to renew and the cost is 3x times the original. Ok so lets transfer it then...nope that cost a ton of money to and there is a 2 month stand down.
So now it is time to setup dns routing, I'll get the domain details go to login in and there is no nameserver or DNS service that cost extra. Very quickly this $9 dollar domain is a $100 domain. You should take advice from your developer or do your research first. If you will be using the domain for anything other than parking it and reselling. You will need DNS and at least Nameserver service.
5) Offshore/Onshore is better
The only thing that makes a domain provider better is how easily you can contact them and how quickly the respond. With most domains you don't end up with issues, but when you do it can be major. You don't want to be up at 2am in the morning, with your website down because of the domain and no way to contact the provide until start of business. I've been there with clients and it never ends well.
6) Does it have whois blocking
As soon as you buy a domain your details go on public record. Now queue the spammers and scammers. If you don't want to be harssed whois protection is a must. It will block your personal details, but keep the contact details legal.
7) If you see SEO advance or hyper improvement
This is almost code for we block the good stuff from happening the charge you to let it happen.
8) If it is from a smaller company or developer
Whats happens if they go bust or disappear. I have had to go on a few long painful missions for clients who have lost the ablity to control there domain. It is a painful and stressful process. Its worth just getting a new one often.
9) Auto renew
If its valuable protect it...put the thing on auto renew. Make sure your email is correct and one you use often. Once you loose it, some scammer will grab it and hold you to ransom to get it back.
10) Where is your domain
For a lot of clients I find it is much easier for them to control one point of access for domain, hosting and email. having your stuff spread out all over the internet can go wrong real fast. Just remember you may not need to access your domain for anothr 3, 4, 5yrs...will you be able to gather all that information up quickly when needed.