A cartouche is a length of rope, drawn as an oval with a knot at one end, enclosing a king's name. The rope is the point: a loop without beginning or end was a promise that what it circled would last. It is also, conveniently, the easiest thing to spot on a wall of otherwise dense carving.
Four signs worth memorising
The sun disc — a simple circle, sometimes with a dot — reads ra. The seated figure holding a flail is a god, often Amun. The folded cloth reads s. The reed leaf reads i. That is not a lot, but it is enough to catch the most common name in Egypt.
Ramesses II ruled for sixty-six years and put his name on more surfaces than any other king, including a fair number he did not build. Once you can read the sun disc at the front of his throne name, you will start seeing him everywhere — Luxor, Karnak, Abu Simbel, and on blocks reused in walls centuries later.
Try it at Luxor Temple first. The forecourt gives you cartouches at eye level and in good light, which is more than can be said for most of Karnak.