Founder, Change The Ratio & TheLi.st (current) Founding editor (media) & first full-time staff writer, Huffington Post (March 2006 - Nov. 2008) Founding editor, Mediaite (Dec. 2008 - Dec. 2010) Adviser, Vox Media, The Muse, Lover.ly, Bustle (current); Votizen, Gui.de (previous). Non-profit adviser to Donors Choose, She's The First & TeachAIDS.org
This depends on your business, of course, but typically you will want to show that you are running as a viable business on the operations side (that you have clear processes and team members have defined roles and responsibilities). You will want to have established your market (i.e. have some customers) and demonstrate an ability to both retain and attract new customers (i.e. grow). If you do not yet have a product that is launched or ready to launch, you should probably show that you are working on an iteration or maybe even a pivot, if you're really not getting anywhere. How a startup deals with failure in the first year often says more than how it deals with success.
Make your deck smart and straightforward - fancy wordplay, double entendres, sarcasm and hokey punchlines do not scan for busy people looking to be impressed. Keep it to your presentation, and workshop any planned jokes thoroughly so you know they work (and you know how to deliver them easily). Also it should go without saying that risqué jokes can backfire and sexist/racist/homophibic jokes will backfire bigtime.
It's only important for the investors to whom it's important. In my experience the more hoops you're asked to jump through by an investor, the less likely that investor is to invest. Creating a business plan is a good exercise though, and worth carving out time for as an exercise in planning and projection. But for very early stage startups, so much is going to change that a demand for a sophisticated, detailed plan doesn't really make that much sense. I'm all for results first.
Advisors and investors are two very different animals. An advisor typically gets an equity stake in exchange for providing ongoing guidance, introductions and actionable advice. This equity typically vests over time to keep the advisor engaged in helping the startup. An investor provides capital, and a *good* investor will provide capital plus everything an advisor can offer. Investors are more likely to view your company favorably if they see that you've lined up quality advisors to help your startup succeed. I advise a number of equity-backed startups and have made numerous investor intros. Happy to chat on a call.
Yes, you need a pitch deck, and yes, make it good. Investors want to be blown away by the opportunity, and by you as the person with the vision to make it happen. Eight slides is optimal - make the opportunity clear at the top so it's obvious what problem you're solving and why the market needs it. Every meeting with an investor is a review - take their feedback and keep iterating. There are tons of great examples online - do a deep-dive and see what kinds of templates and tone work for you. I advise startups on their comms all the time, happy to discuss.