This article is from the Radio Control (R/C) Flying FAQ, by Shamim Mohamed firstname.lastname@example.org with numerous contributions by others.
Since a sailplane has no engine, it follows that it must always sink
through the surrounding air. The trick then is to find some air that's
going up faster than you'll sink through it... and for our purposes,
there are two kinds of such air:
---air heated locally will tend to rise. The heating could be by the
sun on a parking lot or a bonfire or a .... This is called "thermal
soaring"---the columns of rising air are called thermals. This needs
some skill/experience, and mostly involves smooth flying and a good
idea of how your plane reacts. An easy way is to just follow more
experienced fliers (some of which are birds) into them.
---wind striking a slope will rise to go over it. You just fly in front
of the slope where the air is going up. With a steady wind this is
easy to fly in, with challenges provided by aerobatics etc. This is
called (surprisingly) "slope soaring." Landing is more challenging
while at the slope unless you have a large field or something at the
6' or 2m class: (recommended)
Carl Goldberg Gentle Lady, Dynaflite/Craft-Air Drifter II, Airtronics
Olympic 650, SIG Riser, Great Planes Spirit, etc. These are all
polyhedral ships with rudder and elevator controls. All are highly
Carl Goldberg Sophisticated Lady: basically a souped up Gentle Lady,
it is in general not recommended---it's heavier and the T-tail
structure is very easy to break, even on a slightly rough landing.
100" or standard class:
These models fly better but are more cumbersome to launch and transport,
and are also slightly more expensive. Try Dynaflite/Craft-Air Butterfly,
Airtronics Olympic II, SIG Riser 100 etc. These are basically scaled up
versions of the 2m ships above.