This question is so newbie and ridiculous that you might want to put down your drink so it doesn't come out of your nose when you laugh at it.

But are there any warning signs that you're overbeating your mix?

I'm trying to make the switch from boxed cakes to scratch cakes, and I think I'm being a little dainty about it.

I'm making the "100 year old golden butter cake": http://www.babble.com/best-recipes/edgar-allan-poe-birthday/

The instructions say "Add the flour and milk alternately; the flour in three parts and the milk in two"

Well, I did that so carefully that when I looked up at the clock I had spent 25 minutes doing it.  I'm guessing that I probably overbeat it.  (It's in the oven right now, and there are so many bubbles it looks like a witches cauldron.)

I don't suppose there's a general rule of thumb, is there?

AI cannot simply and directly answer your question, unfortunately. Too many individual factors. If you start researching the net your question, or even on CC, you'll get many opinions, all varying. One persons swear by is another's no no. End result of your cake is the best judgement you can do. Do the recipe again, but quickly do the flour/wet/flour/wet/flour addition. Quick like dont have all the flour mixed in before you add in more wet. As soon as the final addition of flour is well incorporated, stop. Make sure all other variables are the same to the 1st cake. Treat your cakes the same after they are baked. Sample them side by side. You will then have 1st hand knowledge of the results and how you like it better and what to lean towards next time. If you have not done so already, Rose L.B. and Shirley Corriher both have very detailed, science behind the baking type cookbooks that also might help you. I have found most people are very willing to help you "test" and compare! You can lift your pinky while you eat the samples and be dainty then! tough texture and tunnels are what you will typically find, but not exclusive to on an over mixed cake.

Thanks Rfisher... I guess that's one of problems of a forum... I always fantasize that it can make me as good as a professional baker, without putting all the hours of learning through experience that the professionals put in!

I guess there's a reason a good baker is good -- they bake!

I'll try the faster combining.  (The cakes I did turned out realllllly filled with bubbles.)

Thanks for responding!

AI would spend some time watching people bake cakes from scratch. There are plenty of videos on YouTube. Martha stewart, baking with Julia, and joy of baking are some that I would recommend to start with. After 25 minutes, you should have had the cakes in the oven and the dishes halfway done! Ok maybe after some more practice... ;) But I think by watching someone else's techniques, you will be able to develop a feel for how things should come together.

Btw...a sign of overbeating your cakes is that they rise too high and then deflate. The extra air makes the cake structure unstable and it collapses on itself. You may find that it seems to take forever for,your cake to bake or the middle seems gooey long after it should have been done. Unfortunately, by then it's too late to do much about it. (This just happened to me last weekend, with a cake I've made a hundred times, so there's always more to learn! :) )

One sign of over-beating your batter can be seen once the cake has been baked and cooled. If you've overbeatened your cake after the addition of flour you will see what is called, "tunneling." You'll see bubbles/holes in your cake (...or as my teacher would like to say, "little worms").

 Here are some examples:

oh man, I had big old worm tunnels -- thanks!

Sassyzan -- that's a good idea... and who doesn't like to watch julia?