I'm not saying you need a super cool homepage with heaps of images. Sites like this are generally a pain in the arse to use and take ages to load. Look at the most popular websites on the Internet: Google, YouTube, Yahoo. Their designs are all relatively simple, and almost instantly, you know exactly what the website is for and how to use it. These are probably the most important things. If a user can't work these things in a matter of seconds, they're going to leave (and probably not come back).
No Splash Pages
Why? Because they're annoying and search engines will consider this your homepage - this is bad. Most of the time, the splash page is nothing more than some cool graphic which has almost no information about the site. If an impatient user has to click through an extra page just to get to your site, they might get frustrated and leave (I'm not joking!)
A search engine bot might do the same thing. If it thinks your site is of low quality, it might only look at a few pages. If your website's homepage has no useful information on it, there is a greater chance of this.
Instructing Bots
There are ways to give search engine bots special instructions (which they'll appreciate, they must get bored working all day with no one talking to them). One way, is to create a file called “robots.txt” in the root directory of your website. In this file, you can set certain instructions. From where your “sitemap.xml” file is, to telling certain search engine bots not look at some folders or files. Two important things to consider when writing a “robots.txt” file are: the bots could ignore your instruction and, anyone is able to view this file and see these instructions.
Meta Tags - Your Keywords & Descriptions
So you've got the basics of what a “robots.txt” file is. But there's more! You can also put information in the HTML code of the page. In between the tags, you can insert tags.
For example, these are the meta tags for my homepage:
These tags are all pretty straight-froward.
* Keywords - Comma (,) separated keywords (or keyphrases). Try to keep the list at 10 words or less.
* Description - If you set this, it will be shown as the page summary on most search engines
* Robots - In this example, it basically translates to, “you're allowed anywhere, index everything and follow all the links on my page.” (Not supported by all search engines)
* Revisit-after - If the search engine thinks you page is important enough, it might listen to you and come back to re-index you page according to the value set here. (Not supported by all search engines)
* Author - I don't think this really does anything. But just in case, I set it. :D
Give It A Name (Using tags)
Like I've mentioned previously, your name should match you domain name and that should match your keywords, blah, blah.
The name of your page is also a very important factor. Not just your pet name for it though. I'm really taking about the text that appears between the tags. Just like your description, the title tag should be accurate and share keywords with everything else. If you can make you keywords, description and title appear a few times in your pages, excellent!
Submit Express have a great tool for checking the length and relevancy to the page for your meta tags and title tag.
DomainTools will also give you an indication of every thing's relevancy to the page. Try DomainTools' SEO Text Browser too. It will suggest things you can tweak to make your website more search engine friendly.
What about the other webpages?
You should use the meta tags and title tag on your other pages too. If you have the time, go around and make them different and relevant to the contents of the page. This is really only necessary if your pages contain different information and you want them to show up on different searches.
What I usually do is set a meta description on my website's homepage, but don't for other pages so search engines will show my pages' actual content on their results.