I learned to dilute 1:1 for most meds. I don't know about state standards, but here's my opinion from my experience:
1. Dilute ativan - it is very oily. Doesn't matter how much NS to add, usually 5ml (unless you have a patient actively seizing - you want to stop the seizure, and adding NS is trivial; also, use a larger gauge needle to draw it up because it is very thick).
2. Dilute irritating meds (such as phenergan, which some facilities have already banned). Diluting lessens the irritation, and I'll use 10ml NS or more.
3. Dilute meds if the volume is less than 1ml and if it also needs to be pushed over more than one minute. For example, Zofran comes in 4mg/1ml and is given over one minute; its easy to control the rate and I give it straight up. However, if I give dilaudid 0.5mg (0.5mg/.25ml): that is a very small amount to try to push over 1-2 minutes (nearly impossible to consistently administer 0.25ml over 2 minutes). I will dilute it with maybe 5ml NS; it is easier to add NS as volume to control your IVP rate.
4. Don't dilute Valium, and if you give it in a running IV, use the port closest to the patient. The medication precipitates in NS and also reacts with the tubing material causing less medication to get to the patient. Therefore, give it at the closest port to the pt as possible (also, if you give valium IM, it needs to be administered in the deltoid, not the VG or DG site). Look it up in your drug book, then ask the teacher (the one who said that every med needs to be diluted in 10ml NS). Make sure to show her that her valium should not be diluted.
5. I never dilute Lasix - you are trying to get the water off, not put more on. You give it very slowly (10mg/1min) and usually I'll have orders for 40mg (4ml over 4 minutes - it is manageable).
I have a PDA and I look up how to administer meds that I don't routinely give. It is very helpful, because contrary to what that teacher says, not all meds are diluted. She shouldn't be teaching this "10ml for every IVP" rule - the rule should be to look up the correct way to administer each medication, since formulations change and the way drugs are given change with research.