- You can escape gravity just by jetpacking vertically up on Minmus. Try it, it's hilarious.
- Docking is a pain in the ass but you need to master it if you want to have an easier time landing on other planets and getting back with everyone alive. Otherwise, make an incredibly efficient rocket that doesn't require refuelling.
- Landing on Mun and getting back is hard enough. Landing on Duna and getting back makes landing on Mun like fruitcake.
- A particular Kerbal giving you problems? You don't like him? He insulted your wife? Give him a one way rocket trip to the Sun.
- Do not use Drogue Chutes on command modules without main chutes (Quill18 video)
- Jeb will probably be the Kerbal that gets killed the most in every beginner's game. He will also revive after a few days.

- A central fueltank won't automatically transfer its fule to the lateral fueltanks and their engines, even if they are in direct contact. You can do a manual "rightclick" transfer (right click on every tank, and then click the empty or fill button of one of them), but seriously, don't try it in the middle of the liftoff thrust, unless you love tumbling rockets.

Or even vertically, if you climb high enough. The fact that you're light enough to get all the way up there doesn't mean you won't die if you cut your jetpack and fall to the ground.

But yeah, with the low gravity and the lack of atmosphere, it's really easy to liftoff, pick up too much speed, and kill yourself when you try to jetpack over long distances on the Mun.

Don't give up. Achieving orbit is the first big step (you did get to a stable orbit?). Many of the other acomplishments seem easy after that :)

- this game likes fast clocked fully functional cores, at least as of 1.0.5. Its ignorant of SMP. If your CPU core is slower than 2Ghz... ouch.

- don't build anything with more than 150 parts. See above.

- play Linux x64 version, at least as of 1.0.5. You can install Linux on any hardware.

- install KER, KAX, KIS, KAS, OPM, TweakScale, KJR, [x] Science!, ScanSat, Waypoint Manager, USI-LF and NearFuture, DrJets (just for Lead Weight - uboats, juhu!). Every single of them is huge gameplay improvement.

- don't ever touch MechJeb, unless you finished carrier mode and was on every planet. Don't! Even after, you won't need it. Really. I am serious.

- learn the four vectors like your five fingers.

- learn what HN+JKLI with RCS on and Locked view mode do.

- learn what happens when you rotate your ship exactly being at 47k Periapsis point to Kerbin. You will love airbreaking!

- to deorbit safely, if you have no wings - rotate constantly, if you have wings do it like cobra. But never have periapsis higher than 200k and never ever burn retrograde between 55k and 25k. Not fried, but smashed.

- to meet someone - go in his direction, rotate to him, then cross him at some point. To get slower, burn retrograde from target, to get faster - burn directly at target. Excercise orbital rendezvous to get within 10 meters by just using navball on map.

- engines work more efficiently if they have less (useless) weight...

- Nm matters in atmosphere, ISP in space

- suicide approach - is most efficient

- assemble your first orbital station! With screw driver! In space!

- if you have orbital bot - you fly by wire - make sure to attach a single very basic solar panel somewhere. This 50$ thing may save your whole ship.

- girder around steering wheels are much more robust than roller wheels.

- test how weight affects max Apoapsis of your ship. How aerodynamic cone affects it. Learn to build asporagus rockets. Then forget that and learn how to build single stage re-usable rockets.

Install the CKAN client. Then install some mods. My basic set
- Kerbal Alarm Clock. Missions run on very different timescales: you can get to LKO and back in a day, a Mun or Minimus flight may take a few weeks, interplanetary missions take hundreds of days. So when and on which mission is your next maneuver? This helps keep tabs on everything.
- Landing Height Display. Cockpits have radar altimeters, but sometimes you don't have a cockpit or it's horrid (Mk2). With this installed the external view displays altitude over ground in surface mode (but ASL in orbit or target mode, watch out for automatic switching).
- Navball Docking Alignment Indicator. The minimal thing to make docking not a pain.
- Plane Mode. Fluently switches between rocket-style (x axis is yaw) and plane-style (x axis is roll) controls.
- Navball Up Default. Anyone else find it annoying always having to click the navball in map mode? Apparently, so here is a fix.
- Stage Recovery. Stock does not really let you build reusable multi-stage rockets, which is a shame. This handles the simple cases, more complicated ones such as launcher planes may require FMRS, which I haven't yet really tried. Saves you quite a bit of cash as long as you put enough parachutes on everything.

Also look up "pendulum rocket fallacy" on Wikipedia. Gravity is not a factor in stability. It is mostly about aerodynamics, for rockets as for airplanes. More about drag than lift for rockets, there being less of the latter. Unfortunately drag is more difficult to estimate during construction.

You can build single stage to orbit rockets.
1) Single stage: OKTO, panel, batteries, fuel, engine, fins
2) TWR at least 1.4 when loaded. *
3) Fuel at least 3400 dV. *
* easy to check with Kerbal Engineer Redux

That rocket propells payload into orbit, detaches it, and lands - powered or using parachutes(default).
Nothing is ever detached from it - no boosters, nothing.

The idea is land close to KSC. If you do 90%+ recovery, the flight cost is 10% of regular rocket.