Secret agent gals
There you are...stuck for an idea (again) of what to give your gal. Although you've put some serious thought into this, everything you've come with up so far was a miss.

When this happens to you, it's unlikely that you're going to have a sudden epiphany and pull some great gift idea out of thin air. Stop wasting time with that and instead, enlist some gals to help you out.

Primary assets
Ask some of her girlfriends and close family members (not the guys) if she's happened to mention anything that she would like to have. Trust me. They'll be overly happy to help you out...not so much because it helps you, but because it benefits your gal. This is a good thing, but there's a pitfall you need to watch out for.

The good
If these gals can list some things that she's specifically mentioned to them, then you've struck gold. Write them down before you forget them. Then organize these items into three categories...(1) gifts fit for holidays and important occasions, (2) inexpensive items you can use as "just because" gifts, and (3) basic necessities that wouldn't make for good gifts at all.

Now, you've got a supply of ideas that you can refer to at the appropriate times.

The bad
I hope it's obvious that items in the "basic necessities" category are things you should't be wrapping up in a gift box to slip under the Christmas tree.

You: "Congratulations! I got you these plain white socks 'cause you told Wendy that yours are all full of holes!"

Her: "Um...thanks?"

Just because she told her girlfriends that she needs something, it doesn't necessarily mean that she wants it wrapped up as a gift. Go for the gift-worthy items instead and let her pick up the basics on her own.

The ugly
Now, once these agent gals finish listing everything they can remember your gal has mentioned to them, they'll probably want to start speculating as to what other things she "might like." Be careful with this particular information though, because it didn't come directly from your gal's mouth. There's a chance that they may come up with some really good suggestions...but it's also possible that their ideas could turn out to be duds.

Even worse, some of them may try to nudge you into buying her something a little more on the expensive side (whereas she might very well be very happy with a more moderately priced gift). Just be aware that this speculative information may not be all that reliable. In the end, use your brain before making your final decision.

Reuse this tactic
Once you've had some success with this tactic, you can certainly use it again in the future. If you enlist these gals for help on every gift you buy her though, they'll pick up on your pattern.

From then on, there's a good chance they'll start talking with your gal ahead of her birthday, anniversary, and holidays about what gift ideas they should relay to you. This would benefit you because you would always end up getting her something she actually wants...and it would benefit her in the same way (she would always end up getting something she actually wants). This situation seems like a win for everyone, but there's a huge drawback.

Don't overuse it
Using this tactic for every gift essentially sets up a mutually-agreed-to scam between the two of you that allows her to pick out out her own gifts. The result of this would be that her gifts would start to feel less special to her, as there would be no mystery in them. Rather, you should save this tactic for those occasional times when you're absolutely stuck for a good gift idea.

Last thought
Once in a while, your gal's pals and family can be helpful with gift ideas. Just be sure to separate the reliable information from any wild guesses they may toss your way.