The "meat" - the "bulk" - the RMS for lack of a better term. 0dBVU on the VU meters (if there are any). That should give you around -18dBFS.
Hard to establish with snare and kick hits due to the extreme transient, so in those cases *even lower* would be the norm. But considering the transients, digital peaks around -12 should give put you in the ballpark if you're working with fairly decent preamps. Lower if they're more "budget friendly" units.
So I want to record a nice 'hot' signal, but only have it show up at like -18 in CEP?
-18dBFS *IS* a nice "hot" signal. THAT'S A NORMAL INPUT LEVEL (where do people come up with this "overdrive the preamp" stuff?!? Honestly!!! Where did it start?!?). 0dBFS is anywhere from around 18 to 22dB *OVER* -0dBVU (which is where the preamp is designed to work). That's not how the system was designed...
For the uninitiated, you WILL NOT get "louder" recordings by recording levels that are too hot. For the most part, the added distortion and lack of focus will make it so your recording
won't have the potential to handle "commercial" levels when it's finished (as "commercial" CD's weren't tracked with their input levels all 18dB into the headroom of the preamps causing noise and distortion on every single track).
You WILL however get MUCH better sounding mixes (that will handle the "abuse" in the mastering stage FAR better) if you track using "normal" levels.
Go on - Experiment. Record something really hot and then recording the same thing using -18dBFS = 0dBVU. Mix them both using the same scale.
Then ram them both into a limiter.
The one recorded with "normal" levels will easily sound better, clearer, less noisy, less "pinched" in the stereo image, etc., than the one with the "hot" levels.