Social kissing is a potential minefield and is usually dependent on situation, age, background, profession and your relationship.
As a general rule, don't kiss people you don't know. Don't kiss colleagues. Do kiss close friends and dates.
Women routinely kiss other women and men and women may kiss one another, without it denoting anything more than a social interaction. Some men now kiss socially, but kissing is rare amongst the older generation, within more traditional professions or in very rural areas. Older men may find it embarrassing and associate it with over-exuberant foreigners.
Social kissing varies according to the age of the people involved. Older people may not want to be kissed at all and even if they do not mind they often only expect one kiss. The double kiss, which is usually the man kissing the woman’s right cheek first, is the norm among younger people. An air kiss, with no contact at all may seem rude or impersonal, but at least it is not intrusive. At most, cheek skin must make brief, light contact.
The key is to make your actions clear to avoid embarrassing confusion. Usually it's right cheek first, but prepare to change direction at the last minute. Pull back decisively (but don't be too abrupt) if you are just giving one. Be cautious with those you are less familiar with - two might seem over the top.
If confusion occurs over one-kiss-or-two, take charge and go in for a second. Humour is useful in deflecting embarrassment over the meet-in-the-middle mix-up.
If you really object to being kissed by people you hardly know then you may extend a straight arm and offer to shake hands, which should give a clear message. Do not force kisses on people who do extend a hand as a sign. However, if you're part of a group introduction where social kissing prevails it is more polite to conform with group behaviour.