First impressions are powerful. The first two-three minutes of the presentation are the most important. Don't waste time rambling on too long about superfluous background information of personal/professional history.
The three rules of structuring presentations are:
1.Tell them what you are going to tell them:
This is the opportunity to get the audience's attention.
2. Tell them:
This is the main part of your presentation and therefore should be allocated the most time.
3. Tell them what you told them
This should include a brief summary of what you have talked about.