When I was in highschool and college, the acrylic nail was touted as the best: This is where they attach a false nail to the end of your own nail and then fill it in with a hard solution. It can make your nails feel a lot stronger (and thicker).
The classiest look for them was, of course, the french manicure. Now, I don't think acrylics will go away anytime soon, but there are certain ways of wearing them that will look outdated. For example, while there is nothing wrong with a french manicure, it's more "in" right now to do a solid look and if you want more the french feel then do a light pink or even a solid white on your whole nail. If you like them really long, try the pointed look to be super trendy.
-Gel Nails - these are basically the same as acrylics so there's nothing really to differentiate here.
Okay, as you may have guessed, this is my current favorite. A gel manicure is a regular manicure in which they use a polish that is thicker and hard. It is not a regular polish, it is a gel consistency. This allows you to showcase your own nails but have your color last a lot longer than a regular manicure. I can stretch these out to about 3 weeks if I have to (and if I go to the right salon), although, depending on the color it will go longer or shorter. Square is still in as is the pointed nail. I have never bought one of these kits to try at home because I really am not good at painting my own nails. =) These manicures typically run around $25 a session which I think is pretty reasonable. Some people have said that this gel color leaves their nails weakened afterwards. If you are not going to be doing this regularly then a tip to avoid weakening your nails is do not pick at the color when it starts to come off! Soak them in acetone, scrape it off and then buff your nails (or pay $5 to have them take it off).
-Regular Manicures - I think any manicure will never go out of style and while I have done these before (typically if I'm doing a color that will look dirty soon - aka, white), I know that the color will chip after only a few days and it's not worth it to me to keep going back weekly. (Also, I love that the gel color makes my nails a little thicker and stronger so that they don't break as easily.) As a Mom, I'm pretty hard on my nails. =)
So, that's my run down of the different kinds of nail options out there. Here are a few random tips to keep in mind:
-Shorter, clean, nicely painted nails will never look out of style. =)
-White nails are super hot right now but it will look dirty faster so maybe don't pay for a gel color if you are just going to want it off in a week.
-Black nails are still really in although they are more of a fall and winter look
-Any light, nude color is extremely classy and will make your hands and arms look longer and more graceful (a bright color will not do that for you as it breaks up the overall look from your arm down your hand).
-If you like it, the pointed "cat" nail is something fun to try.
-Pick a color that will compliment the colors in your closet
-French is okay if you love it but it's a tad "outdated" at this point =)