Hi, Tanja. I don't add a whole lot of extra stuff to my melt and pour, but I do sometimes like to add a bit of ground oats, honey, or clay. I usually add stuff like oats when the soap has cooled some, like 115-120 degrees F. (Honey I may add sooner to make sure it gets warm and incorporated.) If you add your oats and pour your soap when it's too warm, the oats will sink to the bottom. If you want your oats suspended throughout, it's best to stir the oats in and pour when the soap is cooler and starting to thicken and feel tacky. If your soap gets too thick and gloppy, you can nuke it in the microwave in short (maybe 10-second) bursts until you get the consistency you like. Also keep in mind that smaller particles are easier to suspend than larger ones, so ground oats will suspend easier than whole oats.
Here are some threads from a while back about adding things to M&P:
viewtopic.php?f=6&t=1436viewtopic.php?f=6&t=1985The SoapQueen TV videos are a great place to start if you are new to soapmaking. I learned so much from them!