You've already got some good advice, but here are a couple of tips to bear in mind.

Research some keywords - but don't force them into your copy, look at how you can review sentences to include them at the edit stage.

Hitting the return bar is very important! Keep paragraphs short to make them easier to read online.

Write as if you are speaking, keep things conversational and whenever possible use the simplist, appropriate word you can.

For press releases - write in the 3rd person. XXX announces, not We announce

For sales copy - open with questions

hope this is a help