Recently I talked to someone who asked me, "how do you help a child with mild autism?" The term mild autism does not appear in the DSM. From what I can gather this is a term people are using (along with high functioning autism) to describe people on the spectrum who meet the criteria for autism but have higher functioning skills.
No matter what the child's diagnosis is, the first step to helping them is to carefully look at the evaluations used to diagnose the child. Evaluations contain a wealth of information specific to the individual child. Evaluations can help you choose appropriate interventions. For example, most likely you will be working with a Speech & Language Pathologist. If their evaluation states that the child has primarily pragmatic or social language impairments look at social skills groups or products that address this specific area of language delay.
On the flip side if in the evaluations you notice a reoccurring comment like "the child is overstimulated by busy environments" you may want to look into sensory integration therapy. If you notice this reoccurring comment and it doesn't seem to be addressed ask the people who evaluated your child, "how can we address this?"
However, the best advice I can give is this: don't get caught up in the label. At the end of the day its important to remember that each child is a unique person who has unlimited potential, needs love, lots of encouragement and acceptance.