WordPress offers several very nice features which make managing comments a breeze. First on that list is Akismet. It is automatically included on every WordPress.com blog and as an installed plugin on every installed version of WordPress. This wonderful tool will deal with 99.9% of the comment, pingback and trackback spam headed for your blog. For the few spam comments that do get through, when you mark them as spam, they are added to Akismet's database and will be caught the next time.
WordPress.com users don't need to do anything to set up Akismet. It's ready to go as soon as you are. Installed users will need to obtain an API key from WordPress.com before you can activate the Akismet plugin. The key is free - all you need to do is register an account with WordPress.com then go to your profile and retrieve the key. Insert it into the Akismet plugin on your blog and it immediately goes to work.
For the rest of your comments, your options are available in the Discussion area of your blog's Settings.
From the Before a comment appears section, choosing the "Comment author must have a previously approved comment" makes it easy to manage commenters. You will only need to approve a person the first time he leaves a comment. After that, all additional comments will be automatically approved. This option has worked well for me.
The Comment Moderation section can be used to add additional restrictions to be handled automatically. I have mine set to push a comment into the approval queue if it contains more than 2 links. This doesn't limit commenters to 2 links, but it will make them wait for me to look at them before they are visible on my blog. I can also include lists of words usually found in comment spam to push them to the approval queue. I, personally, haven't had the need to do that - not yet anyway - thanks to the Akismet plugin.
The Comments section of your WordPress admin workarea lists all your comments showing the commenter's name, URL, email, IP address and actual comment. You can click the Awaiting Moderation link to view just those comments. Each comment has an option menu to the right of the comment details allowing you to approve, mark as spam or delete that comment. You can also use the checkboxes in the left column to select multiple comments and then click one of the buttons located just above your list.
In the image above, notice the Akismet Spam (4) item just above the Managing Comments title. This tells me that the Akismet plugin is currently holding 4 spam comments. Click on that link and you will be taken to the Akismet list. You can scan the list for legitimate comments - I have yet to find any - before clicking the Delete All button to permanently remove them from your comments collection.
Notice that I do not require commenters to be registered users to leave a comment. I could, but then I'd have to manage a user list of commenters (installed WordPress). For hosted sites, this option requires commenters to have an account with WordPress.com. I'm not trying to collect names for marketing purposes so I don't use this capability on my blogs.
I enjoy the interaction of comments on my blogs. It's one of the main reasons I use a blog platform over other content management systems. Thanks to WordPress, I can enjoy those comments without wasting time dealing with comment spam. I like that.