Hello, good question. I've prepared many decks in my time and reviewed hundreds (maybe thousands by now) to help entrepreneurs with seed through A-Round fundraising.
There are standard questions which must be answered in any basic pitch deck:
Solution (How it Works, Why it Works)
Market Opportunity (TAM, TOM, SOM)
Market Position (Competitive Situation)
Sources of Revenue (Business Model)
Leadership Team and Strategic Advisors
Barriers to Competitive Entry and Exit (Moats)
Roadmap and Timing to Revenue/Payback/Exit
Ask and Offer (Structure, Form, ROI expectations)
It's important to cover all the bases. It's also important to distinguish between the deck you send in email (text heavy) versus the deck you deliver in person (text light).
Generally, you want to lead with your strongest elements. For example, if the market opportunity is huge but you're missing some key leaders or strategic advisors, then lead with your product-market fit and make your ask about the people you need to fill in the holes (before asking for $$).
A really great practice is to distill your pitch down to 1-2 pages, often called an executive summary. Another great practice is to develop a high-quality pitch video which can be sent in addition to your executive summary.
It's also a good idea to prepare a dealroom for your prospective investors, which will help you to keep materials current. Online dealrooms can be free (dropbox, Google) or paid. There are several good subscription sites which will track who looks at your deal materials, when they look, how often they look at each piece etc. This kind of investor CRM is invaluable to the entrepreneur.
I hope that's helpful. Feel free to reach out if I can be of further assistance.