What follows is a quite long list of things I think are very important when you are starting out with your own product business. It is intended to help you avoid mistakes that I have already made (and to remind me of them in the future).

The marketing side

• Your website has one job
  Gain trust from your visitors by helping them with useful content so they eventually join your mailing list.
• Do not focus too much on social networks
  Lots of Facebook fans and followers on Twitter are good for one thing: To drive traffic to your website. But what you really want is people joining your mailing list instead of following you on social networks.
• Treat every subscriber/customer like it's your only one
  Personally I hate companies and people who are only interested in getting new customers and forget about their existing ones. Try to treat each and every customer/subscriber like he's your only one.
• Talk with (not to) your subscribers
  A subscriber is not someone who sits in the back row awaiting the command to buy your products. If you take them to a conversational level instead of just pushing content on them, you gain lots of very valuable insights.
• Things grow by sharing
  You may have heard of Basecamp's (formerly 37signals') advice of emulating chefs. Holding things back does not make sense. Share your tactics/experiences/code!
• Do not base decisions on feelings
  While you are probably part of your audience, you do not represent them. So if a product or feature seems obvious to you, that does not mean that your audience will like it. Do not base your decisions on feelings, research instead!
• Competitors are not your enemy
  Someone who has a product similar to yours or publishes a newsletter which could also be interesting for your subscribers is not your enemy. From my experience, the bootstrapping community is very friendly and supporting - try to get in contact, maybe the both of you can profit from having similar audiences.
• Be persistent
  I am not the guy who tweets a lot. But trying to tweet at least once a day and getting into the rhythm of publishing an article on my website each week has helped me to stay connected with my audience.
• Work towards the immediate next goal
  As a developer, I love refactoring code and refining background jobs but these things do not take your product business further. If you have a family and a day job, your time is limited so every step you take should get you closer to your next goal (be it more people joining your mailing list, buying your product or signing up for your SaaS).
• Don't save products for later
  Work on your best product. Do not try to have a secret master plan with products building on each other because things will turn out at least slightly different. I was searching for a build-up product preceding my ebook for weeks before I started writing it, because I wanted to make it a paid product. If I had not released it for free, I would have barely any subscribers now.
• Remove distractions from important pages
  If you want visitors to take a specific action, you really have to make that action prominent (if you take a look at my ebook-page, there is no footer and no sidebar so besides navigating away, all you can do is get the free ebook).

The technical side

• Keep it simple
  Even the simplest solutions will get at least a bit more complicated as you start implementing them. So (as it is with building great software), focus on iteration: Strive for the simplest working solution, you can always come back later to tweak and refine.
• Build your most important components rock-solid
  The single purpose of my website is building trust from my visitors by helping them so they eventually convert to mailing list subscribers. While I can live with CSS glitches in some ancient version of IE, subscribing to my mailing list must work at all times. That's why the bigger part of my test suite is concerned with just that and I even took the care to make subscribing relatively smooth without JavaScript enabled.
• Have a working mobile site
  About 15% of my visitors come to my site with a mobile device. While mobile browsing is not as tedious as it was a few years ago, you owe it to them to make the mobile experience as pleasant as possible (there's no need to build a mobile site, making your website responsive with CSS goes a long way).
• Make your CTAs really prominent
  As my mentors already know by now (I'm looking at you, Mr. Hillman), I have a tendency for unobtrusive CTAs. If you want a visitor to click a specific button, this button has to really stand out from the rest of your content (using color, size or whitespace).
• Have a dedicated page for your mailing list
  When someone asks how to join your mailing list, you do not want to tell him to open your website, select a blog post and scroll to the bottom until your subscription form pops up. You want a single page dedicated solely to joining your mailing list so you can give people the link. Preaching water and drinking wine, I still do not have such a page on my website.
• Know your visitors
  Know at least some things about your visitors by using a tool like Google Analytics or Piwik, but try not to get obsessed with analytics data - you do not want to spy on your visitors, you just want to track important events and find out what your most popular blog posts are.
• Backup
  Having a handful of shell scripts (or recipes for you favourite provisioning tool) and frequent backups of your database ensures that you can get from zero to a working website in basically no time when your server blows up.
• Take hosting seriously
  If you don't want to run your own server then choose your hosting provider wisely - don't just use the cheapest one.