It's very important to check keyword competition and volume before you proceed.
You might always have heard that content is king in SEO. Make sure your webpage doesn't have duplicate content.
If you put keyword repeatedly on your website you can never rank for that. It black hat SEO tactics that can hurt your SEO. Keyword density should be in between 2% to 4%.
Every time in some interval of time new algorithm update comes. You have to be aware of all updates and follow them.
It is considered a black hat SEO technique. Always make quality and relevant backlinks.
Do proper analysis from time to time to find out broken links and try to fix them either by removing it from the webmaster or by 301 redirection.
Most of the peoples are complaining about SEO rank. They just follow old techniques and building spammy links. I hope it is clear that what are the factors that are hurting your SEO.