cover all the bases
Refers to where you behave responsibly during all of the progression through the various stages of intimacy, taking appropriate measures to protect both of you against undesirable things like infection or "accidental" pregnancy.
The best ways to "cover all the bases" with a new romantic partner are:
First base (i.e., hugging, holding hands, foot/back-rubs, etc.): Taking deeply-cleansing showers beforehand, brushing teeth, trimming hair and nails, etc.
Second base (i.e., kissing, close snuggling, sharing non-intimate full-body massages while wearing just a bathing suit or undies, etc.): Taking all steps described in "first base", plus using breath-fresheners, antiperspirants, soothing and/or aromatic oils, etc.
Third base (i.e., French kissing, naked cuddling, intimate massages, sleeping together, etc.): Taking all steps described in "first base" and "second base", plus having easy access to a warm/cold shower at all times, keeping the bedroom a comfy temperature, etc.
Fourth base (i.e., handjobs/blowjobs, "going all the way", etc.): Taking all steps described in first three "bases", plus having plenty of condoms and/or personal lubricant handy, keeping tissues and damp wash-cloths within easy reach to clean up "messy" aftermaths, having changes of sheets and pillowcases to put on the bed if necessary, etc.
First base (i.e., hugging, holding hands, foot/back-rubs, etc.): Taking deeply-cleansing showers beforehand, brushing teeth, trimming hair and nails, etc.
Second base (i.e., kissing, close snuggling, sharing non-intimate full-body massages while wearing just a bathing suit or undies, etc.): Taking all steps described in "first base", plus using breath-fresheners, antiperspirants, soothing and/or aromatic oils, etc.
Third base (i.e., French kissing, naked cuddling, intimate massages, sleeping together, etc.): Taking all steps described in "first base" and "second base", plus having easy access to a warm/cold shower at all times, keeping the bedroom a comfy temperature, etc.
Fourth base (i.e., handjobs/blowjobs, "going all the way", etc.): Taking all steps described in first three "bases", plus having plenty of condoms and/or personal lubricant handy, keeping tissues and damp wash-cloths within easy reach to clean up "messy" aftermaths, having changes of sheets and pillowcases to put on the bed if necessary, etc.