Lessons learned the hard way...

[-Gamah]

Never try a crazy mission plan without Jeb.

[cardgame]

Don't forget to burn retrograde.

[vexx32]

Start your burn before periapsis when first attaining orbit.

[Nikolai]

Don't try to land skinny craft on hills.

Don't set try to set trim prior to launch.

Don't play with a cat anywhere near your computer.

[Markus Reese]

Lock stages = Alt+L. Hope that saves you some trouble.

Did not know...

You sir, are a hero amongst men

Also, learning the hard way: Remember to install rcs thrusters after I waste the weight on rcs tanks....

[bsalis]

- Staging. Sometimes hilarious, such as first stage having unactivated SRBs decouple, then slowly topple over as the the rest of the rocket slowly lifts away on liquids.

- Forgetting the decoupler between the command module and the tank under it.

- Not testing parachute setups.

- Consistently saving an aircraft upside down after working on the underside then launching without flipping it over.

[Vanamonde]

Before switching to a landed ship, make sure you've zeroed the throttle.

It landed door obstructed, and the remaining weight was too great to turn it over. So ended my first mission to Duna's northing ice cap. RIP Matlie Kerman.

[lucidLemon]

Before switching to a landed ship, make sure you've zeroed the throttle.

It landed door obstructed, and the remaining weight was too great to turn it over. So ended my first mission to Duna's northing ice cap. RIP Matlie Kerman.

Before zeroing throttle, make sure you've landed.

I've killed far too many kerbals this way.