I don't use a lens hood most of the time even though I have one for my main lens. For me its an issue of stray light entering the picture vs portability. Lens hood usually pretty bulky unless yours can fold. I bring my cam around daily in a smallish work bag which i put my other work stuff in, if got lens hood not much else can go in. But of course if I go out just to take photos with my nice big 7 million dollar home then the lens hood goes on.
Your choice--portability vs image quality. If the former is not an issue for you, then by all means there are far more pros than cons for using the hood.
I was told that for long lenses (28-200mm), a hood is very helpful. Had difficulty finding the original Canon hood so that's why I thought of a third party. But I think I may have found one at one of the shops. I'll be checking with them tomorrow. Thanks to everyone who shared their tips in this thread. It has really been helpful.
using hand or card/s is recommended if you suspect stray of light from dominant source. be sure it does not stray into yr lens coverage. i learnt a long time ago, that putting yr eyes very close to the lens and another hand or card/s to block extraeous light is good practice, especially doing studio still lifes. actually, in this circumstances, black cards and gobos are recommended. hands not reliable.