Essentially for an overnight bag you will still be allowed your clothes, slippers, toothbrush, alarm clock etc. What you will have to watch out for is sharp blades (scissors, razor blades on their own),"liquids" eg after-shave, deodorant, lip balm, toothpaste (under 100ml tube), bottle of refreshment.
Your "Liquids" have to go into a clear sealable transparent bag no larger than IIRC 8 inches square and with a capacity no greater than 1 litre. No individual liquid/paste can be in a bottle/container capable of holding more than 100ml. (A document pouch from a High Street stationers may suffice).
You can take an empty bottle greater than 100ml through, then fill it from a water dispenser once through security.
You can take a camera etc through so long as (a) any internal battery is fitted,and (b) any spare batteries have their terminals covered.
You cant take a laptop or electronic tablet through but it will have to come out of your case for the security check.
Medication: Prescription medicines should have the dispensary label on them. Liquids/pastes will usually have to go into your 8 inch clear pouch. Check that any medication is permitted in your country of arrival as well as country of departure to avoid being arrested.
That should cover most eventualities.....
Happy travelling and safe flying !