I suggest you start with checking out some Pitch Deck samples of well-known companies. You should easily be able to find pitch decks of companies such as: Airbnb, Tesla, Facebook, Buffer, Square, Linkedin, etc -  check out this link. 

Before you start designing the pitch deck for your startup, make sure to cover all sections such as: 

• The problem  
• Solution  
• Target audience  
• Market size  
• Revenue model  
• Competitors  
• Some stats  
• Timeline
• Marketing strategies  
• Everything else 

Try avoiding long paragraphs. Make it as simple as possible so that the potential investors are well-aware of what you're offering. Also make sure to keep it summarized.