Actually writing a bid is not that difficult at all. You need to understand what the client actually wants and then translate it into paper by giving your competencies and strengths. Here is a link from where you can see how to write a bid along with several examples:
www.rfp-templates.com/search/for/How-to-Write-a-Commercial-Bid.html
www.rfp-templates.com/search/for/How-to-Write-a-Commercial-Bid.html