Your first order of business is to know what your needs are. Look at this with the big picture in mind, and do not just restrict your needs to the present moment. Although you may not need a lot of different resources to get started, if you plan to build a big business you are going to need them later on. Look for a provider that offer the features that you could need in the future. This will avoid the frustrations that can come with changing your service later.
Support: This is something you will need the most. What kind of support the web hosting company provides the clients such as telephone support, email, FAQ sections, etc... Maybe a dedicated discussion board or forum will help as well. Also check on the delay in responses especially for the email support service. A web hosting provider who supports clients 24-7 is an excellent feature.
If you already know exactly what are the features you will need to build your website, you simply have to look at the feature list that is always provided by any hosting company. (If they don't provide their features list, I don't think you should go with them! ;) ) The most important feature to look at is: do they support the coding language you want to use? You'll also want to know if they have mailing list, databases and email forwarding services. Except that, like most of people you don't know every little things that you'll need. That is why I always recommend to choose the web Hostinger hosting provider that gives you the most features. You never know if you'll need them someday and that day, you'll be very happy to have them because you won't have to change your host.
Once you are signed up with a company to host your web site, then log into your account where you registered your domain name and change the nameservers to point to your hosting company (the hosting company provides the nameserver information you will need). This is fairly simple, but if you need help the first time be sure to call the company where you registered the domain name and ask how to do it. They should be happy to tell you.
Storage is the next major point. You need to know you'll be able to fit everything for your site into the allocated space. IF you run out of space, you wont be able to fit any more web pages or images in. This is a Bad Thing(Tm). You need to make sure you have at least 5MB for personal sites, 10-20MB for basic business or 50MB for advanced and corporate websites.
Last but not least: Price - I used this as a motive in the beginning, but I have seen that price should not be the limiting factor. You can get hosting from check here just $4 up to any limit you wish. Choose wisely, and stick with a host for long term, it is much wiser to pay a little more than to build your business on a penny platform.