What are some tips for throwing a surprise party?

I started planning a 50th birthday party for my mom recently and she just came up to me and said that I should throw her a party since this is an important age for her. I don't want her ruining the surprise!!! What can I do to throw her off?

First don't tell her otherwise she won't be surprised.
Secondly, ask all her friends and your relatives to do the work otherwise she will know something is up or something is different about you. Also, ask her friends and your relatives not to go overboard since you don't want your mother in the hospital from a heart attack.
Keep the party simple and easy.

Suggest a quiet elegant dinner for her at a venue of your choice and on your way there, conveniently forget something to be picked up at her house so that you have to bring her back.

Tell her about the party, but tell her you are having it a few days after the day you are actually throwing the party. Unless she is smart, and I mean like genius smart, she will fall for it. I tried this once, it worked great.

Tell her you have something you absolutely cannot get out of, scheduled for the date of the party you are throwing. Then offer to host a 'party' on a different date.
Make sure you have some reliable person who can bring your mom to the party site. Someone she would not suspect of being in on surprising her.

We are doing this for my mom's 80th.

Plan two steps ahead with an ambush.

Act really secretive so she starts suspecting something. Leave an "accidental" clue somewhere- have someone leave a voicemail, leave a slip of paper in your pocket, whatever- with plans for a party on the WRONG date.

She'll think she's so smart, and then when you really surprise her, she'll be amazed. Good luck!

Keep it a secret.

tick her off around the time of her birthday. get into sum argument idk