Organising a surprise party can be very exciting! Especially if it is for a close family member or a close friend. It can be quite expensive but there are plenty of ways to keep yourself in budget and not spend so much, and of course, keep it as a secret!
You will need too choose a venue that is quite easy to get too. For example: If you tell the person you are taking them out for food, you will maybe need to book a venue in that place or a place near the restraint. If you know someone who owns the venue or know someone who does then you can see if you can get discount? But I would look around and get prices first before you book.
Go for a theme the person likes. Weather it be 80's, 90's, Pink etc. You can shop around online for things like this such as Amazon and Ebay or other online party stores. If you weren't looking to pay for delivery then maybe you can pop to town one day and look for decorations in shops there.
Write down who you're going to invite. Maybe it would come out cheaper if you do your own personalised invitations. With it being a surprise party you should write on the invitation that it is a Surprise Party and for them not to tell the person who you are organising it for. Make sure to invite as many people as you can to how many you have catered for in the venue.
You could make your own birthday cake for the person. If you've got no idea where to start, look on Google and You Tube tutorial videos. They will give you ideas and tips to make a great cake. There is no need to spend loads on a cake when you can do it yourself and it will be more meaningful.
If the person lives with you then you may have to tell them a little white lie and say you're going out for a bit somewhere, and you will have to maybe go somewhere or to the venue on the day to do the food for the surprise party. It may be best to cater for just a little bit more than the amount you have invited.
Keep It A Secret
For it to be a surprise party then you need to keep it a secret! You have to try your best to give no hints away. If you think you know anyone who can't keep secrets then maybe you could leave their invitation until a couple of days before the date.
These tips are my own opinions and from my own experience.