Disk Space
All hosting accounts offer a certain amount of disk space that you can use to store all your files. Exactly what is, and isn't counted towards your disk space usage will vary from host to host; so make sure you check exactly what files you will need to allow for when deciding how much disk quota you will need.

It would be a good idea to have some sort of estimates on what you need for various tasks. How much space will you need for storing your email, web files, databases and log files? By breaking down your usage like this it will be much easier to work out how much space you should go for (once you know exactly what files are counted towards your disk quota).

All plans will certainly include all your web accessible files when calculating disk usage. Some hosts will also choose to include email and/or logs in the quota, which can make estimating your disk space requirements more difficult. While you may have a good idea of the disk space needed for your web files, your email and log file needs change constantly.

Should a host include all types of file storage in the quota, check to see if you can switch off your logs or exclude particular information. If the option is available it will save you a lot of disk space, particularly if you have a busy site. However, if you want to use any statistics package that is available with your hosting, you will need to allow some logging to take place.

If you enable your logs then it is also worth remembering that you might not be able to delete a log file from the server until the server has stopped writing to it. Daily logs are fairly manageable if you remember to log in and download and delete them regularly. Problems with monthly logs can arise if you underestimate your log space needs and you can't delete the file until the end of the month; which could lead to an extra charge if you aren't careful.

If your email settings and inboxes are included in your disk quota, it might be an idea to set the maximum size of each mailbox if it is possible. This will save you from storing too much mail on the server and inadvertently going over your limit.

Email Accounts
Email accounts are a common feature of hosting, particularly if you are hosting a domain. Some hosts will let you have control over your mail settings, putting restrictions on mail activities (for example the number of accounts or maximum size of mail boxes) on the server side. Other hosts will do all the set up for you, even though setting up of new mail accounts can be easier than you think with the right software support.

How you configure your email is a matter of personal preference, but there are essentially four main types of mail accounts; POP3, forwarding, aliases and autoresponders.

POP3 accounts are the traditional "inboxes", you have space on a server to store your mail, allowing you to use an email program to log in and download your mail; each login and password combination usually equates to one account. This works a bit like an office inbox, the mail is left there until you do something with it; if it is full then your mail can't be stored and bounces.
Forwarding mail accounts are useful if you want to send your mail to a service like SpamCop or other email filter before you receive it. Rather than store it on your mail server, it will redirect all mail to another single email address where it is dealt with appropriately. This kind of account is useful for redirecting your emails to a common POP3 box.
Aliases are names that can be used to identify different types of email account, redirecting them to POP3 mailboxes on the server or other addresses, where they are processed again if necessary. What happens to the emails will depend on whom they are being sent to. A catch all alias is often used to collect and deal with email sent to people or departments not recognised by your mail server.
Autoresponders are not an email account in their own right, however they do have their own email address and simply reply to anyone that emails them for information. They are useful if you want to send out pre-prepared information to people requesting it, as opposed to you replying to all the requests manually.

FTP Access
One other thing that is common amongst paid hosting accounts is FTP access. FTP programs allow you to upload files and to edit and delete your content on the server much more quickly than using a web-based interface. If you are hosting on a *nix system, you will also be able to change your file permission settings using FTP.

One of the better features I've seen offered with hosting, is the ability for you to create your own FTP accounts. This is great when you have someone helping out on the site or if you want to share your web space while keeping your user's files separate from your own. How hosts go about this can vary.

Some hosts will let you act like a mini hosting company, where FTP accounts that you create takes them to a special users folder specifically for their files; keeping them from your main files. Other hosts will allow you to create FTP accounts that you can define exactly which folders they have access to, and exactly what they can (and can't) do with them.

While having the ability to create multiple FTP accounts may seem trivial if you don't intend to host other sites on your web space; it can be useful for allowing temporary or permanent access to anyone helping you with your site, without you ever needing to give out your own FTP account details. Now that is a feature worth having!