All the above are useful as a general guide. Below are some "mastery/achievement tips".
One thing I've noticed is that you can depower the shields until the Zoltan shield is down. This frees up yet another energy point for weapons or dodge. Personally, I put it into dodge, as it means when you do need the extra energy back to the shield, you don't risk resetting the cooldown.
Also, Ion does double damage on the Zoltan Shield, so dodge is 100% your best friend.
Finally, if you're going for the "No Extra Power till Sector 5" Achievement, you wind up saving tons of scrap (as there's no point buying extra slots). Buy cloaking ASAP. It's 300% more effective than the equivalent power going into the engines, and it keeps your Zoltan shield up longer (see the first point for why this is a very good thing). Another useful feature is level 2 Oxygen, as it means you can spend lots of time with it completely unpowered, then burst it on full for a few seconds when you get near suffocation.
Obviously, for the 29 power in systems, you need to be on the lookout for another Zoltan crew member. They're rarely handed out as event rewards, so always have enough scrap available for them at a store. Also, avoid the "Great Eye", "Spiders", "Mantis Pod" and "Dead Station" events, as they kill random crew-members. You also need to focus putting money into systems to get up to 29 slots there.