I am looking for some advice with making microfoam. I have a magister stella machine. When I try to make microfoam, I end up doubling or tripling the volume of the milk by the time it hits maximum temperature (I am using a thermometer), and I get a layer of foam on top of a bunch of hot milk. Are there any decent guides out there for doing this?

Thanks in advance

Lots of discussion on this. Results from a search for the term "microfoam":

Frothing Milk for Cappuccinos and Lattes - Espresso Guide

Microfoam and other beginner questions

Milk gets too hot before I get stretched milk

Latte art, marshmallow issue

Is there such a thing as "too much microfoam"?

Problem getting perfect microfoam without any air bubbles

Microfoam half-life -- optimal combinations of milk type and temperature

I could go on. Read these and others. Practice. It will come with time.

Great thanks!

There's also lots of videos; I searched "steaming milk video" since that's a more common phrase than microfoam. It yielded some good results like How to Steam Milk for Cappuccinos and Lattes and Learning latte art with steamed soapy water. There's also national barista champ Lem Butler's instruction that was part of the Newbie Introduction to Espresso video series:
Returning to your opening description, you're clearly stretching the milk too much (i.e., injecting too much air). Simply bury the steam wand into the milk sooner and focus on rolling it. That will assure a more consistent mixture and avoid overstretching. It will also help to use a larger volume of milk. Some beginners make the mistake of economizing on milk by steaming tiny quantities in small pitchers. While that can be done by a skilled barista, it's much easier, for example, to steam 9 ounces of milk in a 20 ounce pitcher than 5 ounces in a 12 ounce pitcher.

If you're still stuck after watching a few videos and reading up, post a video of your routine. As Lem mentions in the video above, it's not hard to diagnose the problem by sound alone.