the general rule of thumb most people follow is to make sure any liquids, even a tiny bottle is in your hold luggage. toiletries and deodorants of any size are allowed in your hold luggage, snacks and goods up to a certain sterling amount in line with the particular airports restrictions (we're talking around a £1000 worth of food and drink so no need to worry on that!) do not need to be claimed at customs so you walk right through.
basically if you can avoid it, do not take any liquids into your check in BEFORE security, purely to save yourself time and effort (if you did you have to put every liquid into seperate, clear 100 ml bottles and even there I'm not sure if you can take more than one). obviously if you have a baby, then formula is fine but you would need to proof what it is at security as others have mentioned. if you are unsure at all, ask the security people, they are there to help you

I once had a panic as I take the pill, and I get travel sickness so I had my travel tablets and my pill and had no idea on the rule of over the counter and meds. so I asked the guy checking my bags and he said it was absolutely fine and to always ask if I'm unsure. they're mostly a friendly bunch and would prefer you to get through quickly than not knowing what to take and what to do.
any snacks and small bottles drinks you buy in the airport after going through security is allowed to be taken on board as you have had no time to tamper with it in anyway. however, as mentioned above, buying perfume or any alcohol on duty free is not allowed if you're flying outbound. I wasn't allowed to buy any perfume a couple
of years ago as I could tamper with it whilst at disney, but I was allowed to buy whiskey for my dad at paris duty free coming home as I would have no time. leave any airport presents for others or yourself that is liquid till you come home basically