I like Link 3 the best. To get a ring for her you could always buy a larger band and then have it resized later. Talk to the jeweller when you go into the store about resizing. They can give you tips on the best styles that will work with resizing, and also give you options.
Just a warning. When you hand a girl a box which she will know is a ring box her brain goes from 0 to 100 in milliseconds. It can become very awkward as she can freak out thinking omg he's proposing- this is amazing/this is not good. So maybe take it out of the box and put it in something else
I like 1,2, or 3. It really depends on what you want to say with your gift. As far as how to get her ring size. You could see if she had any other rings, ask her mom or someone else who might know, or take her to a store and look at some stuff and see if she wil try something on.
I like number 2 best. To get her ring size can you take on of her other rings? Your best option if you can't get one of her rings is go bigger because if you need it sized it is cheaper to make it smaller then to make it bigger.
Find someone who has similar size hands as her? and usually they exchange it if it's not the right size (ask them when you buy it if it's possible) or you can take it somewhere else where they make it to her size after you give it to her.
& I like link number five. :]! with link number two. :]!
Ask a friend, not the kind who you know loves gossip but the quieter type who will keep your secret a surprise. If your in her room, you could swipe one quick and outline the inside of it on a sheet of paper so you can take it to a jeweler.
idd get her a size 5 because you can always have it made smaller or bigger and size 5 is the best size to get adjusted... my mom works in a jewelry store but ummm if I were you idd go with 5 is so perfect idd cry if my boyfriend gave me that
I like one but that's just me as for her ring size try one of her rings on your fingers and try to remember which finger of yours it fit on or the more logical one is to take a ring of hers and trace the inner side of the band with a pencil and take that with you.
I chose link one (the earrings) but mostly because I don't wear necklaces that often. What you get for your girl though is totally dependent on what you think she would like, of course.
As far as finding out her ring size...does she have a mom or sisters or any girl friends available that could help? The other answerers are right...if she has any rings you could sneak, you can get them sized at a jewelers! (or you could just make an educated guess and she can always get it resized)