Guageing Sparing Intensity

Anyone have any tricks for guaging how intense to go
when sparring? I've moved to a new town, and am
starting to look for new gyms, and will eventually
get back into sparring.

I tend to always start too light and too relaxed, so
I get run over by young bucks who have less skill
but more enthusiasm. However, I hate being "that
guy." The one that's always going too hard, or the
new guy at the gym who looks like he's got something
to prove so he makes an ass out of himself. Still,
I don't want to embarass myself, my former trainers,
and anyone else associated with me.

for new guys i usually start peppering with jabs and i tend to let them hit me with the first hard punch. in response i throw a hard punch right back. i find this brings out the truth in what they want to do, either they will respect you and stop throwing hard punches, or throw another hard punch in response and thus the cycle repeats itself.

as for the more experienced guys: i do the same thing as i do with new guys but i don't hesitate to be the first to throw a hard punch because the more experienced guys know how to deal with it and how to respond, whereas the new guy is most likely still learning.

No matter the scenario i always get the guys respect first i.e.
give them one good shot first and then work from there.