Thank you for your replies it really helps. Sevencubed where does that number 2 links per 750 words comes from ?
There is one thing that you said that I don't understand but maybe you can explain. If I create a link you that says diamond watches, watch <a href="example.com">repair</a> and link to my homepage knowing that I don't repair watches I don't understand how it can help search engine and the user ( the user by clicking on repair is going to expect a page about repairing watches and this not what he or she will find ) and I am sure what will be the benefit for the search engine ...
By the way should the word repair be in my homepage if I link like that ?
How many times should I have the exact keyword in my external links is there percentage recommended or maximum ?
How is the value of internal links versus external ?