Maintain self-confidence. Just because you're older, doesn't mean you have to be inhibited about flirting or about your desire for love, sex or attention. Projecting self-confidence is an effective flirting tactic at any age.
Dress well. Aging takes a natural, unavoidable toll on one's body, but dressing well can help keep you looking good. Moreover, it clearly signals that you care about your appearance, which many consider an appealing trait. Wear nice, clean clothes appropriate for the occasion.
Remain socially active. Engaging in different social activities not only provides you with a variety of outlets in which to flirt and meet people, it also keeps your social skills sharp and gives you more to talk about when you do encounter someone with whom you'd like to flirt.
Avoid masquerading as someone you're not. Mitigating the effects of age with a bit of makeup is acceptable, but trying to fit into clothes that looked good on you at a younger age and no longer do is not attractive. An older man or woman who is accepting of his or her age is sexier than someone who seems to be in denial about it.
Engage in affectionate gestures and playful touching. This is a time-tested flirting tactic that works well for the old and young alike. Respect normal boundaries and the fact that not everyone is comfortable being touched, but don't let age scare you off from the kind of light-hearted touching and innocent yet flirty contact that expresses interest and makes people feel desired. Older people (especially those who haven't dated in a while) may particularly crave the affectionate contact of someone else.