Kerbal Space Program

Let me start by saying that I'm no expert on the subject. I now have around 1,700 hours of play time, but I really started achieving SSTO after 600 hours lol...
My advice for really getting started would be as follows:

• Start small, and without any payload. It's easier to make just a small plane capable of going into orbit.

• If you respect the previous advice, then ONLY use R.A.P.I.E.R. They're very powerful and will get you into orbit with just one or two engines.

• For your first flight, avoid MK2 parts. Despite their appearance, the drag is dreadful. Use the classic MK1.

• Don't keep your wings all flat, try to make sure your plane can take off without any input (this isn't the case on this ship, unfortunately, but it's better to do so).

• Save weight. If you find you've got too much LF left when you go into closed cycle, take it off in the SPH.

• If your plane can't get above 400m/s without problems at 2km altitude, try a new design.

• After several tests, if you've reached orbit, you can save fuel by following a precise flight plan. Try to find out. For example, my current ship works very well if I stay at 10° during ascent, switch to closed cycle when the engine reaches 20kn thrust, and once my apoapsis is 71km, cut the engine and switch to prograde.