If price is not an issue or if you're just curious but don't actually mean to buy, yes you can walk into a store and pick anything up and plug it in.

But, realistically, when you know you want to buy a guitar while you already have one (or more), you do have some preconceived reason as to why you are not satisfied with the one you have and that dictates which guitars you're more likely interested into. Sometimes it's the price, or the pickup types, or the sound, or the design, or the brand/model, or maybe just the colour.

If you're curious as to how other guitars sound and feel like go into a store, tell them what guitar you have and ask them to suggest a few different guitars for you to try out (different neck width/length/radius, different pickup types and models, different body woods). If there is anything you are unhappy with on your current guitar, it may be worth mentioning too.
It helps if you don't flat out tell them you are not actually looking to buy one soon (because then essentially you are wasting their time). Let them hope.

Thanks. I've wondered how different neck configurations might feel. I have rather short and stubby fingers, so I could use a bit more room between the frets higher up.

I'm afraid not much is going to change up there. The change in spacing is proportional and the difference in neck lengths is not enough to have an impact on the high end. You can only feel the difference on the low end. Also you probably have a 25.5" scale neck which is the standard. The next most common is actually shorter at 24.75". Guitars with longer necks (27") exist but are very few and targeted at people playing in extremely low tunings. Because essentially the neck scale affects string tension more than fret spacing.

Just thought I'd post a follow-up. I stopped in at a music store yesterday and tried a few models out. Just grabbed one from the wall, found an amp to work with, and plugged it in and played with it for a while. It was kind of hard to hear over the sounds of the other guys and a whole bunch of guys trying out some bass guitars. Tried out a Les Paul, three Fenders (a regular Strat, a modified HSS Strat, and a Tele), an Ibanez (7-string), and a Jackson. I didn't think that I'd be able to hear a difference, but there were definite noticeable differences. In the end, I liked the regular Strat the best for the look, feel, and sound. Liked the sound of the Ibanez. I think I'd need to spend more time with the Les Paul to choose it over the Strat.

There are substantial differences between a Strat and an LP. Pickup configuration would be a great place to start. But find the one you're most comfortable with and maybe throw in - what kind of music you play. Necks on LP's tend to be a bit beefier as where Strat necks to be slighter. Don't spend the money until you're ready - it's a investment you'll have to live with a while so be confident in your decision.

The typical LP and the typical Strat (or Tele) are near opposite ends of the solid-body guitar spectrum:
typical LP: short fat neck, flat fretboard, dark-sounding wood, humbuckers, fixed bridge.
typical Strat: long slim nec, curved fretbord, bright-sounding woods, single coils, vibrato bridge.
There are pros and cons for each setup and some people have very strong feelings about one or the other, but both can sound excellent. And of course both Fender and Gibson offer models that have elements from the other side.

The 7-string is a different animal. I'm guessing it came from the RG line. You get very hot pickups, wood with intermediate sound properties, long thin neck, flat fretboard. And of course in this case you get the merciless low end growl of that extra string.

Bring a girl, have her pick out the one that's sexiest on you, buy that one.

Its why you are probably buying a guitar in the first place.

I own 6 electrics and 4 acoustics.....All of which I have never bought without first trying them. Been playing 30 years.

To me, I must try the guitar out first. So walking into a store and taking them off the wall and trying is what I do. Comfort is so important to me as a player. Maybe the guitar looks great, but if it doesn't feel right in your hands, and just not comfortable, then your not going to play it as good as you could. It would probably help if you had an idea first of what kind of guitar you like, from there, you can narrow down your search via different models...ie: if you like Les Pauls, try a few different ones ( Standard, Classic, Traditional, Custom)......if you like Stratocasters, try a few out( Standards, American Deluxes, etc). When it comes to Strats, I have always preffered the "American Deluxe" series over any other kind, but thats just me. Everyone is different. I just purcahsed an new American Deluxe HSS strat, but I prob played 20 different ones until I found this one that just felt better to me.

Good luck and hope you can find what works for you. Have fun looking and trying...thats the fun part.

S.