It depends.
Some people are wired to be uncomfortable with a large group of people but can function well with one or two.
Some neglected social skill development when younger and are now somewhat awkward.
Some actually dislike others and find it hard to mask their contempt.
If you have a desire to become more social, it is like any other skill development program. You start with small steps and as you acquire skills, you move on to larger ones.
The first area of skill development would be with the casual encounter. This is what you have with store clerks or people you encounter in parking lots, subways, and elevators. There is only time for a quick quip, or humorous comment that eases social awkwardness. This is usually a 20-30 second window of opportunity for a unidirectional declarative statement. For example when walking by an mother embarassed holding a crying infant, you might say, "I remember the first time I heard about income tax too." A humerous comment like this can help alleviate the mother's anxiety and can even be appreciated.
After being able to navigate these waters, a person can begin to experiment with bilateral exchanges such as brief comments about the weather, sports, inflation, etc. (politics or religion may be topics for the advanced student)
Mastery (or at least adequacy) of the casual encounter will be key to opening social opportunities for greater social depth. Some general principles for this level are ;
1. Ask questions that show a genuine interest in the other person.
2. Do not talk about yourself too much.
3. Disagreements do not always have to be given voice.
4. Criticism of others can make people uncomfortable.
5. Do not offer unsolicited advice.
The key to experimentation is frequent attempts. The sooner you discover your own techniques that are successful, the sooner you become more proficient.