Being able to strike up a conversation need not necessarily be limited to people who are open and gregarious. Anyone can learn to interact in a friendly manner and with the adequate amount of practice using the appropriate tools.
The simplest way of initiating a conversation is to first establish eye contact. Making eye contact allows the other party to acknowledge and accept the invitation to initiate friendly contact. When this is done then both parties are establishing the interest and so a conversation can be started.
Smiling also helps to open the door to a conversation starter. Most people respond well to the simple smile provided it is shown in a friendly and not in a weird manner. With a smile anyone can pick up a conversation as the friendly and open setting has been set.
Having a reasonable amount of knowledge on a particular relating subject matter is also another way the start up a conversation. It should be noted at this point that the conversation content must be relevant to the situation or scenario. This would not only encourage participation from the other party, it can also be perceived as an impression making tool.
Of course the old fashioned style of simply saying “hi” or “hello” is another way to initiate a conversation. Even though it is fairly simple to initiate most people find it rather embossing to use this method for fear it will not receive a favorable response. Looking presentable is a plus point when trying to strike up a conversation. Nobody really wants to talk to unkempt or unhygienic people.
For some people it is genuinely difficult and stressful to initiate a conversation. There are people who suffer from certain low self esteem issues and this kind of problem can only be addressed medically and physiologically. However in general if one has or projects a friendly image, then staring up a conversation should not really be a huge challenge.