To ensure that your park runs smoothly you need to manage ticket prices, customer satisfaction, and marketing. You will be able to set the ticket price as soon as you lay something down by tapping on it to bring up the the menu and then tapping on the price tag icon. You will find that the ticket prices are set cheap by default and you will be able to raise them a bit without upsetting your customers if they are in the 'Good Value' range.
Keep an eye on customers that have a coloured thought bubble above them as this icon expresses how they feel about your park. A blue thought bubble indicates a customer who is having a good time while a red thought bubble indicates an angry customer who will not return. Another way to check the mood of your customers is to check the satisfaction bars at the top of the screen. These bars will be for Fun, Food, and Hygiene and they are maintained in different ways. Building more roller coasters will improve the Fun bar, having plenty of restaurants will raise the food bar and building lots of toilets will have a positive effect on the Hygiene bar.
Once you reach level 9 you will be given the option to market your park to attract additional customers. This will either be watching an advertisement for a 5% increase in customers for 3 hours or you can buy a 15% customer increase for 12 hours by spending 25 tickets.