The simple and very basic problem people have is having a layout. Well it is very simple, or at least it can be. You must remember:

1. What is the genre of your site?
2. What is the target audience?
3. Do want it to look proffessional?

Above are just simple guidlines. You may have many more, but for me they work. If you look at most great sites (PR 7+) have the standard but very effective layout.

Banner on top, Master menu below the banner, Quick Menu on the left or right, login system along the top, main content in the middle, polls, search. other quick features on the left and the page footer with quick links and copyright information.
Also remember to have some graphics (gradients prefered), but dont go overboard.

Keep your content short and snappy. This is because most viewers just skim read the content. Small sentences mainly, and some long sentences, and keep all of your words on track and relevent to the site.

Try and keep personal (if it is not relevent) details or references out of your site. Try and not put me, or i. You can however put Our, as you can be refering to the overall site/ company.

Sign-Ups. There is nothing more annoying than, sign-up here, click here, then type in here, then go to here, then pay this amount, the wait for an email that will come to you immedietly (that comes like 6 years later). Keep your sign-ups simply but secure. A simple form can change everything. All the details on one page.

Keep to what you say. Have you ever seen on all of these sites, coming soon! And it never seems to come, well after a couple of months it does. But your expecting it to be there within a week or so, they should put: Future Plans. It is more honest.

Please also check your W3C compliance.

W3C Validator

Font. Keep your font simple. It makes it better, easier for people to read. A good example font is Arial, 10px. It is just the perfect size. Also keep a good consistent colour scheme.

Coding. Try to vary your coding types, from HTML, DHTML, XHTML, Javascript, etc. Use the coding that is relevent to your needs.

Finally, always make sure you have a DocType.

Mik

I don't get your tip about varying coding styles. You should use the coding type that works the best for what you are trying to accomplish.

Anyway preach on about the signups Preach!!!

You are right about the coding styles, i forgot to add that part. Consider it added.

Sign-Ups:
Always make sign-ups in PHP. DO NOT USE JAVASCRIPT or any other coding of the sort. They are so easy overcome (basically, 9 times out of 10 you just look at the source code!) If you are going to do a login, then learn PHP and SQL first. You can learn them by going to

Tutorials on PHP

Also remember to give the people who want to sign-up plenty of security information and warnings about your login system. Remember to tell them that certain fields are required to fill out. (what i don't get is why have all the other un-neccessary fields, it's pointless). Also remember to tell them the character limit in each field. Don't put ZIP code only. Have a run-down box, where corresponding to each country is there system: Britain = Post Code
America = ZIP code
and so on.

Keep the login box/ form in the exact same place on all pages. Also provide a lost Password area, where it is secure. For example:
What is your username:
EX1
Wha is your favourite pets name:
Dog2

Also on the sign-up area, remember to tell the visitors tips, like longer passwords are safer, longer usernames are securer and so on.

More tips later.