Many prospective RC pilots come to forums like this one to find out which plane they should buy to get started in this amazing hobby. It's easy enough to get answers on what specific planes to buy. There is even a sticky at the top of this forum with that exact information. Many are happy with that, but it's also helpful to get into the science and the experience that makes these planes good for beginners.

There are a few characteristics that are needed for a beginner plane:
1. Self-righting and stable.
The two go together. High wing planes naturally want to fly upright. A flat bottomed wing (that means curved on top, flat on bottom) will tend to pull itself out of dives, and dihedral (wing is shaped like a V when viewed from the front or back) resists being rolled and will correct itself when allowed to. Good trainers are designed to fly straight and level, and these wing characteristics make them do that. So you want a high wing plane with a flat bottomed wing (or only slightly curved) and some dihedral.

2. Big
Bigger flies better. Skip the little 24-20 inch wingspan planes that are sometimes marketed to beginners. They are ok in an indoor area with the HVAC off, but you'll quickly lose control of them outside. In general, the bigger a plane is the smoother it flies, slower it feels to the pilot, and the more it resists wind effect. Traditionally, balsa planes were sized according to the engines they needed, so a good place to start is with either a .40 or .60 size balsa wood trainer.

3. Lightly loaded
Wing loading is the ratio of the area of the wing to the weight of the plane. A heavy plane is fine as long as it's also a big plane. For a .40-.60 size trainer, a good wing loading is between 17-20 oz per square foot. That will give the plane docile handling characteristics and very gentle stalls. Wing loading is influenced a lot by the plane's construction, but also in your choice of components. As long as you stick with manufacturer's recommendations and don't put an enormous battery or camera gear into the plane you should be fine. But a few planes sold as trainers are on the heavy side, so check the specs.

4. Tricycle gear
Tail draggers have their place in our hobby, but they aren't as easy to manage on the ground. The positive steering of a nose wheel will make learning takeoffs easier.

5. Tractor type prop
This simply means the engine is in the front. Some pusher prop planes (motor in the back) are marketed to beginners. While some beginners have bought them and learned to fly with them, they are a handicap. Tractor configurations can pull themselves out of a stall better, which can let you save the plane from a pilot error.

6. Stable in the wind
This somewhat goes against items 1 and 3. Self-righting planes roll away from side winds which can be quite disconcerting to new pilots. And light planes get tossed around by the wind. So this is a balancing act. If you live in a windy place like Texas, Missouri, Kansas, etc, you should pick a plane will less dihedral (2 degrees is enough) and maybe put a bit more engine on it than is called for. Calmer areas can tolerate the classic 5 degrees of dihedral and lighter planes.

7. Solidly built and easy to fix
This definitely competes with keeping it light, but the fact is some trainers are just too fragile. Common weak areas are the landing gear mount and firewall. Beef them up. And understand you are going to probably ding up your plane while you are learning. Don't buy some moulded plastic plane that you'll have to throw away if it breaks. Simple box type fuselages and balsa wings can be fixed over and over without having to source any special parts. You can even make modifications later if you want.

8. Quality components and field gear
Don't get into this hobby and invest your time only to be disappointed by an unreliable engine, cheap tools, a radio without the features you really need, or junky hardware. Yes, this hobby costs money. But it also costs time. Buying cheap, junky stuff wastes your time and ultimately your money too when you have to replace it or wind up quitting the hobby out of frustration. Save your pennies and get the right stuff the first time.

I'm sure others will have opinions too. I'll ask that the group keep the conversation on topic so this can serve as a concise resource for future RC pilots who want to start out the right way.