I am regularly asked for advice by parents with children on the autistic spectrum. Because autism is such a profoundly complex condition, and very personal in how it affects each individual, it is not possible to offer advice that will be equally insightful or helpful to everyone. From my own experience, I suggest the following:
Ensure good basic hygiene skills, particularly tooth-brushing (which I had considerable problems with over many years into adolescence) and which I've subsequently read is a common problem because of the sound or texture or both of the brushing action.
Help teach your child core skills to function in society: how to dress themselves, tell left from right (perhaps use 'L' and 'R' labels as my parents did with me), maintain eye contact, understand and respect the concept of 'personal space', how to ride a bus etc.
Nurture any special interests, while finding ways to use them to help your child learn more about the wider world (for example, a passion for spelling can be used to discuss the names of family members or neighbours etc).
Discourage tantrums by identifying triggers and finding ways to avoid them (for example, supermarkets can often be overstimulating, try using smaller local shops).
Have patience - progress, if and when it comes, can often be sudden but is the result of many months or years of incremental steps forward.
Most importantly of all, know that your child is capable of great depthes of feeling and of love, even if it isn't much or often demonstrated.