1. Before making your website live, you need to make sure that your website is running fine with or without WWW. You can always make 301 redirection to resolve this issue.
2. Reserve a subdomain for your website mobile version so that you would not have to face any uncompromising situation later.
3. Try not to use dashes in the domain names. However, if the preferred domain has always been registered, you are open to use hypen in the domain name.
4. Perfection is a happy blur in the design industry. Try to comprehend the simple fact that you cannot have a pixel perfect design. After all nobody is perfect in the mundane world.
5. Try to keep the required information in the sign up page of your website to a minimum since people will not care a fig to get registered if you badger their lives with so many questions.
6. Try to reduce size of the files as far as possible as file size has a direct impact on the page responsive time.
7. While designing mobile version of your website, you need to keep it as simple as possible. Do not use flash since iDevices do not offer any support for flash based sites.
8. Try to use CSS and place the codes in a separate CSS file. Do not use inline CSS since it will add to the complexity of your website.