Here are some things I have learned in playing with Instagram.
If you are in a situation where you must shoot fast and not make decisions about filters, or if you are shooting in bright sunlight and can't see your screen well, shoot with the regular iPhone camera. Later when you have time, feel like it, and can see well, pull the photo from your iPhone photo album, crop it and filter it and share it. Just be careful to allow room for cropping the rectangle image into a square.
If you are trying to shoot in the Instagram app but want to zoom, you cannot, so exit Instagram, open your iPhone camera and use that to take the photo. I use this often for shooting city landscapes when I want pieces of buildings but when close objects would ruin the shot. When I'm passenger in the car I can zoom and shoot some interesting landscapes.
Take photos while stopped at a red light. We have some lights here that are 90 seconds long! That is a long time! I grab the camera and take shots of lovely clouds and sunsets as well as cityscapes.
If you are the driver ask your passenger to shoot certain objects you see while driving, that would be unsafe for you to attempt.
If you want to do multiple filters on the same image save the first crop as normal. Then start a second Instagram using the "normal" photo and use the filter. Then repeat. In this way you can get a series of identical shots that use different filters.
Use down time for Instagram. I have filtered shots while standing in line to pay the cashier at stores, while in waiting rooms, and while sitting in my car waiting for my kid to finish what he's doing so I can drive him home.
Using Instagram is so fast and easy. You don't have to do the whole process right on the spot. Instagram should be fun and should not have any pressure attached to it.
Speaking for myself I rarely waste time playing with Instagram, I'm just using up spare moments here and there. It's fun and it actually diffuses the stress for me because it prevents me from getting aggravated at a slow cashier or a forever red light.