It's a good idea to always cast a circle of some kind, yes. But, depending on the amount of safety desired and your skill with certain techniques, casting a circle may be as simple as visualizing the circle and turning with your hand outstretched to make a simple ring of energy.
Meditation is a wonderful thing, because it helps regulate your body, easy away negativity, and focus you. Basically, it makes you healthier, whether you have spiritual intent or not. But it does also open you up to the deities. It can also be a way to raise or generate energy, explaining those others' reactions.
Both are good ideas that you'll benefit from. But I wouldn't recommend using the super-simple circle technique without having quite a bit of skill in energy manipulation, or else you might lose your concentration and be left with a big energy hole in your quickie circle!
"We need each other, more than anyone dares to admit, even to themselves. ... There is no question in my mind that there is nothing else in life, really, than friendship." - Patch Adams
