What is the number one thing a startup founder can do to ensure a seed stage investment?

You are right that the range is wide. You need to figure what are good values to have for your category. Also, you can focus on the trend (is your DAU/MAU increasing vs decreasing after you make changes) even if benchmarking is tough. Unless your app is adding a huge number of users every day (which can skew DAU/MAU), you can trust the ratio as a good indication of how engaged your users are. For games, DAU/MAU of ~20-30% is considered to be pretty good. For social apps, like a messenger app, a successful one would have a DAU/MAU closer to 50%. In general most apps struggle to get to DAU/MAU of 20% or more. Make sure you have the right definition of who is an active user for your app, and get a good sense of what % of users are actually using your app every day. Happy to discuss what is a good benchmark for your specific app depending on what it does.

AngelList is your best bet. Since you're asking the question, chances are you don't have a way to get introduced to these investors. The simple truth (like it or not) is the chances very low that you'll get a deal done without an introduction from someone they trust. AngelList can help with that, so can going to networking events. And finally, If you're the introverted developer type, you can also get their attention by just building something really cool on your own, followed by some serious traction. Arguably the best strategy of them all.

The more important first impressions to leave a VC with are: 1) That you both are credible and inspire confidence that you can execute the plan you're fundraising on. 2) That there is good chemistry and a great relationship between the two of you; 3) That you can adequately address the concerns/objections/questions the VC raises. The CEO is expected to do most of the talking because the CEO should be the best person in the company at articulating the vision and value of the product and company you're building. If your CTO is comfortable presenting part of the pitch, it would be ideal for the CTO to speak to the product slides. The most important thing is for the CTO not to be a "bump on the log" meaning that you don't want them sitting there for most of the presentation with nothing to say. If you feel that's the case, you really shouldn't bring your CTO. Most VC meetings will not get technical and under the hood. Each question answered should be answered by the person best qualified to speak to that question. You should make eye-contact with your partner and use subtle body language to find a way to cue the other person to speak to that question or simply offer "CTO, would you like to answer that?" Bottom line, make sure that the CTO can speak confidently enough about the product and vision, otherwise -unless specifically asked by the VC - come alone. Fundraising is a big distraction to building and a good VC will always respect that in a first meeting, the CTO can be excused from attending in priority of building product. Happy to talk to you both on a call about helping get you feeling a bit more confident and prepared before your meeting. I was formerly a VC associate for a $500m fund and have raised money from VCs as a serial entrepreneur.

If you want information that matters in "Creative Financing Techniques" find a person with the experience/insight. Most of what is in books is dated. Many of the more creative methods are a function of current tax code and market factors (like QE).

I heard of a startup that recently launched called http://sketchdeck.com that has become pretty popular for fundraising decks. Happy to do a dry run of your pitch with you in a call.