Here's one for you: use sub-heads. People often skim through a sales letter (even an online one) and using plenty of sub-heads can often help to get your message through to a speed reader. Now, you don't want to overdo it, but sub-heads usually help.
Copywriting is a big umbrella that encompasses blog writing, web page content writing, article writing, PR writing, sales copy writing etc... Can you be more specific about what you want to know!
Are you looking for tips on how to write for the various venues available to you ...or are you asking about Copyright "law" and what you're allowed to write or "borrow" from others? Like "doubts", I'm confused on what type of tips you need.
You can read useit.com and websitetips.com/webcontent/ > These two are really good. My tip> Step 1. Become a consumer or think from a consumer's perspective.
Read http://www.copyblogger.com DAILY. Subscribe to its RSS feed. I require all my newly hired writers and trainees to familiarize themselves with that blog.
Never copy anything from the internet. don't use the same lines in different articles after u write a article, check it atleast 1 or 2 times for any spelling or grammar errors don't over use keywords
Hi, You can find a few good tips here: http://www.melissadata.com/tips/copywriting.htm Lior Reuveni, Smiley Marketing.
Write to cater to a target market. I posted a free document in another thread. I've been a copywriter for over two decades and I use some form of this document for every project. You must know your target market to be a good copywriter. If you don't define one, you're not a copywriter. Target Market pdf
Besides Copyblogger you can read http://writetodone.com (a newly-born blog of Leo Babauta), http://www.michelfortin.com ("about copywriting, marketing and life") or www.copywriting911.com (yes, that's ours ).