When you feel your child is physically ready to write, have your child use a stick or finger to draw in sand, rice, pudding, shaving cream, paint or oatmeal. Make simple lines and shapes and ask your child to copy them.
Many online math games are designed purely for entertainment and won't do much in terms of teaching your child. While these games can be fun and engaging for third graders, you want to choose games that will practice the skills being taught in school.
Quality worksheets for preschool can help you with a lot more than just academics. For example, once your child starts kindergarten, they will be expected to sit still and complete tasks for about 15 to 20 minutes at a time.
Worksheets also, when used properly, provide both the students and parent / tutor immediate feedback as to the child's progress. This means they can be used to point out areas where the student needs further reinforcement.