Type keyword into google, open page previews of top ten results. Read 3 best pages. Then put it into your own words. If its a product also visit official page and Amazon to get idea of why people like it.
Put keyword in approx once every one hundered words, and similar keywords smattered around too (plurals or KW in different order).
Proof read always (I often read it out loud as if I was a newsreader, as some sentences sound OK in your head but don't flow properly out loud).
Keep sentences short or just one comma in them.
Only use big words to make the product sound good, not in the general text.