So you've discovered the different campers and are now set to do their requests in order to improve your friendship level with them. However, you'll bump into the daily limit of requests you could perform for each animal. After playing the game for a while, you'll figure that campers inside your Campsite can be serviced for 2 requests per day, while those outside your camp can be serviced up to three times. If you want to get past this limit, you'll have the option to use a request ticket in order to refresh that particular animal's request limit for the day.
That said, if you have exhausted all three request of an animal outside your camp for the day, you can use a request to that animal in order to gain additional 3 requests from that particular animal. Take note too that you can use a maximum of 3 request tickets per day for each and every animal friend you have (at least as long as you have a request ticket). This means you can actually perform 12 requests for a particular animal per day if you have request tickets to spare. Otherwise, if you happen to not have request tickets available, you may have to pay 10 Leaf Tickets to earn the same effect of 1 request ticket.