What I have tried to give you here is a range of useful articles on tendering and bid preparation. They cover a range of topics, but at their core you will find issues relating to improving your responses to tenders (RFTs), proposals (RFPs) and quotations (RFQs).
In many cases tender and bid responses are unsuccessful because people don’t understand in full how to go about the tender process, how to analyse, plan and execute a response that has a consistent success rate.
And that's the problem. People start businesses because they are good at what they do; they have great technical skills. But they haven’t had the opportunity to acquire the necessary skills.