1. Disk Space
All hosting accounts offer a certain amount of disk space that you can use to store your files. Exactly what is and is not counted as disk space usage will vary from host to host, so make sure you check exactly which files you'll need to allow for when deciding the disk quota you'll need.
It would be a good idea to have some sort of estimates on the space you'll need for various tasks. How much space will you need for storing your email, Web files, databases and log files? Breaking down your usage like this will make the task of work out how much space you should go for (once you know exactly what files are counted towards your disk quota) much simpler.
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 probably 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 may save you a lot of disk space, particularly if you have a busy site. However, if you want to use a statistics package, you will need to allow space for 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 then find you can't delete the file until the end of the month. This could easily 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 a maximum size for each mailbox if possible. This will save you from storing too much mail on the server and inadvertently going over your limit.

2. Email Accounts
Email accounts are a common feature of hosting, particularly if you host a domain. Some hosts will give you 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 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 storage space on a server for your mail, and you 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, and the mail is left there until you do something with it. If the inbox is full then your mail can't be stored, and will bounce.
Forwarding mail accounts are useful if, for instance, you want to send your mail to an email filters service like SpamCop before you receive it. Rather than store it on your mail server, it will redirect all mail to another single email address which will deal with it 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 who they're being sent to. A catch-all alias is often used to collect and deal with email sent to people or departments that are 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 who request it, as opposed to you having to reply to all the requests manually.

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