First, be definitive
Don't over-qualify statements, make them definitive. Don't say 'I was wondering if...', or 'I was thinking that we should...' Say what you want to say, particularly if it is contentious. Softening the blow of your opinions or demands is counter-productive, introducing an element of equivocation where none exists.
Only if the outcome is genuinely up for debate should you offer it as a question. Even if you are making a request, make it direct - 'I need your help' rather than 'I was wondering if you could help me'.
In a similar vein, don't project your demands and needs into the future: "'I was going to ask you if...", "When you get the chance, could you...", "I want to tell you..." Make the demand, raise the point, ask the question; don't say you are going to do something which you are already in the process of doing.
Second, eliminate constant self-deprecation