When I teach others how to sense using empathy I use about five gemstones.
I cleanse and charge each one to match their most simplest meaning. And pick ones that are very different from each other (in meaning).
If you can't afford many gemstones, a single quartz crystal can be used, but must be cleared of the previous energy before placing another energy into it. This can drain the crystal of its natural vibrancy so I suggest placing it in salt water under the moonlight after training with it.
This isn't a guessing game. I take each one, put it into the person's left hand let them close their eyes and identify with the feeling. I make sure they know exactly what it was charged with because they will help them to identify the feelings later on. I will also place my hands on top of theirs and charge myself with specific energies and tell them what I'm charging with.
If you are good at channeling different energy, you can do this by yourself, but its best done with another person.
You can do this with just about anything, but gemstones are the most consistent in my opinion.
A "burning" or "painful" feeling is negative energy. So if a stone hurts it needs to be cleased more. Negative energy is different for every person depending on their own energy. If a certain energy feels negative to you, and it is consistent, then it could be something that doesn't agree with you. For instance someone very hateful toward love -- someone scorned -- may feel love energy as negative until they can accept it as something "good" again.
This is why clairsentience is a very personal subject. You really need to sense everything you can and decipher for yourself what it "feels" like.