I think it's important to learn how to short, even though you may not wish to do it. Most stock exchange would frown upon shorting and measures had been set up to prevent people from doing naked shorting. That's all well and understandable. However, I think for those who are always on the 'long' side, it's equally important to learn how to recognize short signals.
In the past, I'm more interested in looking out for buy signals because that's essentially what I do. I buy first and sell later. I don't sell first and buy later, which is essentially the meaning of shorting. That makes me very good at buying and finding the right entry. But to fully complete a trade, you must learn how to buy and to sell. I would say that there are so many books on teaching people how to get into a good entry but ......