syngoniums:

Another flower from the Glottiphylum. I think it’s time to move it back to part shade; it’s getting quite red and going limp very quickly. It’s a good idea to get in the habit of gently squeezing or poking your succulents, so you learn how they feel in various states of hydration. Well-hydrated plants are firm to the touch. As they dry out, they may start to feel spongy or rubbery, and even shrivel if very dry, but they do not become fragile and retain a tough “skin”. Overwatered plants that are not rotting may stay firm but split open in places, while overwatered and rotting tissue will be soft, easy to damage and leak fluid. Non-woody parts that are dry and tough may be natural corking, scar tissue, or dead tissue that did not undergo wet rot. You can use a blunt object like a chopstick to prod plants that are too spiny or prickly to touch directly.

I also recommend feeling the soil so you can learn to correlate soil moisture to the state of the plant. If a given plant stays firm for a long time in dry soil, for instance, you will know that it is unlikely to appreciate weekly watering. It can give you clues to plant health; if a plant feels underwatered, but the soil is moist, for example, it may have rotten roots or other damage that is preventing it from taking up water.

Bear in mind that unless you are growing in a very controlled environment, a plant’s needs will vary according to variables like temperature and the amount of light it’s getting. Feeling a plant gives you more subtle info about its status than just looking at it does, especially if you’re new to that kind of plant and aren’t sure what it’s meant to look like in your conditions.