I've considered this question before, as I'm sure many others have. When it comes to meeting with a gal that I've never met before, I approach it from this perspective - you can only make a first impression once. I also usually follow this guideline with gals I repeat with as well.  I don't over dress - usually a nice shirt and khakis.  I once had one gal actually say to me that I didn't need to get dressed up - I didn't think that I was "dressed up". But I told her that I didn't want to show up like a slob. Whether or not she appreciated that, I don't know. In reality, first and foremost, they're only concerned with how the donation envelope is dressed up - with plenty of Ben Franklins in it!  But, regardless, I personally feel it helps to set a positive tone if you show up looking presentable.  For what that's worth, that's my 2 cents.

As long as you are clean and respectful

and your clothing is clean it does not matter to me they are going to come off anyway ha ha!
Truly though my favorite outfit on a guy are jeans ( that hug his ass just a little) a nice cotton breathable shirt , I love to see a guy in a button down cotton shirt but shorts are hot too if worn  
with a shirt that accents his shoulders and chest or everything if he works out. I like tennis shorts
on a guy the less he wears the better! No speedos please !
 

Smart is best...

you wanna make us horny right?  

Sx

Showered

Just as long as your clean I'm sure clothing is optional,)...

That wouldn't bother me .......

........ sure keep in mind the surroundings you'll likely be in but come summer weather I don't think hotels even some of the nicer ones will give funny looks if you "dress down".  
I don't think every guy will be going in and out of a 3.5/4 star hotel in full suit & tie in 85+ degree weather IJS.

I look forward to seeing what a guy has on the first time we meet.  It's part of the anticipation package for me.....  
I would be upset if I found out they were not being THEMSELVES and feeling COMFORTABLE though.   That is THE most important thing.  It's exciting to meet someone new and you shouldn't be feeling awkward or uncomfortable with how you're dressed.  I don't think it's being disrespectful at all to arrive wearing shorts.  After all, it IS summer!!  Dress for the Season!

I love the way certain fabrics feel so if you're wearing one I especially like, I do enjoy running my hands around on your shirt.......    
oh, With that being said, I do have certain Mens-Clothing-Fetishes.

 
1)  I love the "uniformed" look.....military, airplane pilot (OMG, I have a fantasy about THAT), male nurse in scrubs, mailman, cable guy

2) Belts that are super easy for me to undo and flick off with just one hand..... wow, that's sexy

3) A suit and tie Really get me going  

4) Mens shoes

5) and lastly, The CFNM fetish; in the genre of erotica, not the BDSM realm.

I love what maddaddy wrote, and I concur:  If the clothes don't "do it for me" the fingers in me will!   lol, good one....LOVE It

Clean is always important, but here's an alternative scenario with a question at the end:
It's a brutally hot summer day, 98 degrees with humidity to match. Fresh from a shower, you drive th her incall, then walk just one block to get there. By the time you arrive, you are soaking wet with sweat.
Will your lady allow you to shower once again at her place? Will it be on the clock? Or, is there a difference between sweat from working and sweat from weather?
What say you, ladies

Good question!

As long as you are dressed for the occasion (ie no shorts on a dinner date), and your clothes are new (not threadbare/stained), clean & crisp, I think casual attire is fantastic. Some nice denim and a button down can go a long way...  

However, asolutely no sweat pants!! Ha.