Assuming you would like tips on how to surprise someone you haven't seen in a long time:
1. Find out what they have been up to- Obviously you can't surprise someone if you don't know what they are into nowadays. Try and catch up on their social media, talk to mutual friends, or even ask them directly what they have been up to. This will give you a better idea of what kind of surprise they would appreciate.
2. Make it personal- A surprise is only good if it is tailored to the person you are surprising. Something that is significant to them will make the surprise that much more special.
3. Keep it a secret- The element of surprise is key! If you tell them about the surprise ahead of time, it takes away from the impact. Try to be as sneaky as possible so they are completely caught off guard.