If you're using a ziplock bag, be sure to keep a few extras in your carry-on in case it rips open. It happened to me once and there were no extra bags at the security checkpoint. One TSA agent wasn't going to allow it through since it wasn't sealed but a supervisor let it go.
I like buying sample size containers from drug stores (especially if they are rectangular shape and close to the maximum allowable size). I fill them with my own products and they are already labelled (i.e. I put my shampoo in a shampoo bottle, my conditioner in a conditioner bottle, etc.) I have never had a leak reusing them but I have with empty travel bottles that I purchased.