Many of the children I work with have global development delays, including social-emotional development. Here is an excellent hand-out for parents and caregivers to understand what a 2-3 year old child should be doing in the area of social-emotional skills:
Although parents of children who receive an early diagnosis of autism seem to be aware of their child's delays of social-emotional skills, my experience is that parents of kids with no diagnosis or a diagnosis other than autism don't seem to be as clued into this area of development. Many times the parents assume the child isn't playing with his peers appropriately because of his language and/or motor delays. But kids with delays in those areas often still play with their peers okay if that is the only area of delays. I think many kids have to literally work on these skills listed in this link. That might mean that a child with no siblings who stays at home with his mom all week, be exposed to other children on a regular basis such as going to the same park on a regular basis as well as to story time at the library, playground in the shopping centers, and MDO (mother's day out) program for 1-3 days a week for 5 hours each of those days. Play dates and play groups are also good especially if the child doesn't have other neighborhood kids to play with or young relatives that he sees on a regular basis. If all of these strategies still do not help, then an evaluation with a psychologist, occupational therapist, or speech therapist may be necessary. Another good suggestion is to receive a comprehensive evaluation with the local early childhood intervention (AKA EI or ECI) program which will evaluate and work with children up until their third birthday. If the child is almost 3 years old or older, then an evaluation by the public school could be beneficial. Also, look to see if your area has an early headstart program with any openings.