1. Photos! There are so many times I've been at a crop and someone has actually forgot her photos, yikes! Help yourself out by keeping photos on a service like Google photos. It's good for more reasons than just if you forget your photos. They are precious, make sure you always have backup.
2. Adhesive! And not just a little adhesive, take a lot, it's the one thing you are most likely to run out of. Make sure you have your tape runner, pop dots, glue dots, a glue pen and maybe even a Xyron.
3. Paper Trimmer! Don't forget spare blades too. You aren't going to get very far if you don't have your trimmer with you.
4. Scissors! Bring both a small sharp pair (non-stick) and long scissors. It's very hard to cut straight with small scissors and difficult to cut intricate projects with the large ones. You need both.
5. A Good Black Pen! Even if you aren't big into journaling, outlining, marking sizes, and just taking notes are all reasons you need a good pen.
6. Ruler! Okay, maybe you are not obsessive about things being straight but a good ruler will help you line up photos and mats, help you cut just the right size, and give you the perfectly drawn straight line.
7. Hand Lotion! I recommend the Udderly Smooth brand. When you are handling paper the moisture in your hands gets sapped away. Also, most venues for crops have very little humidity in the rooms which further dehydrates you. You'll need lotion and this type absorbs quickly and doesn't stain your paper.
8. Cup Holder! For one thing it helps with space if you hook your cup on the side of the table instead of taking up precious room on top. Also, spills happen, don't let them happen to you. If it contains a garbage bag too, even better.
9. Snacks! I know this sounds simple but the truth is, even if people bring snacks to share, YOU know what snacks work best for you, whether it's your favorite candy or if you like to stick to healthy snacks. Unless there is a sign up where you can see what snacks are being brought, make sure you have what you need.
10. Realistic Expectations! Before you goal, decide what you want to get out of the weekend. Is it to finish pages or is it more about socializing. Do you want to organize or take classes. Once you've decided your objective, pack accordingly and take it easy on yourself. If you don't get 50 cards done, it's okay! It's more important that you had fun!