First of all asking before taking a shot often ruins the natural scene you want to capture so dont do it. Best way I have found is to use a fairly long lens so you can take the shot from some distance (this is the reason many photo journalists use 70-200 lenses). You may be noticed but because your a good distance away the subject is rarely too affected by your presence. If your presence is met with concerned looks the best thing to do is smile broadly before moving on. This tends to put your subject at ease. Very occasionally you will get someone that really does not like being photographed but this is very rare and in those instances a quick chat will normally calm everything down. If you feel shy about taking these types of photographs then the only solution is to just get in there and start doing it. The more often you do the more comfortable you will become in these scenarios. The more you push the boundaries of your comfort zone the larger your comfort zone will become.

First of all asking before taking a shot often ruins the natural scene you want to capture so don't do it. Best way I have found is to use a fairly long lens so you can take the shot from some distance (this is the reason many photo journalists use 70-200 lenses). You may be noticed but because your a good distance away the subject is rarely too affected by your presence. If your presence is met with concerned looks the best thing to do is smile broadly before moving on. This tends to put your subject at ease. Very occasionally you will get someone that really does not like being photographed but this is very rare and in those instances a quick chat will normally calm everything down. If you feel shy about taking these types of photographs then the only solution is to just get in there and start doing it. The more often you do the more comfortable you will become in these scenarios. The more you push the boundaries of your comfort zone the larger your comfort zone will become.