My mom and my sister are planning my shower in February. They told me the date, time and location, and I sent them a guest list at their request. Aside from that, I have no involvement. I did request that I get to do seating arrangements (we had some awkwardness at my bridal shower which I want to avoid.) Its at a restaurant with 10-top tables. I didn't want one of my friends stuck alone with my mom's friends, or vice versa, wanted to group family together, etc. I figured showers are often a nice time for people who haven't seen each other in awhile to socialize, so I wanted to make sure they got to sit with who they are comfortable with. I went to a couple showers this year and I really appreciated the seating chart.
Frankly, I don't even want to know everything else. I am looking forward to the surprises of the day.