Have backup slides for common questions, and prepare a reference list in advance. Efficiency in both plan and presentation will create a good impression that often is taken as a proxy for how you will run your business. You get one shot in front of your prospective investor. There are no dress rehearsals. Thou shalt thoroughly research and evaluate current and prospective competition.
All startups have competition of one sort or another.
Thoroughly map out the competition, and honestly assess your relative status. Openly disclose the management team's background strengths and weaknesses. Today, marketing and sales execution is more important than ever. Thou shalt get real about financial projections. Investors understand that financials for new businesses in undefined markets are very hard to estimate, much less verify, but be realistic.