Or, more fully: How can you be a good GM while also being able to participate in the roleplaying aspect of the roleplay?

In 1x1s and small group roleplays, a GM also is (often) a character and part of the story - not just someone running things. I really like that aspect, though I am sure others perhaps will disagree or have different preferences. But the couple of times I attempted to run things like that on my own, one of two things happened:

1.) The RPers went all gung ho, inventing monsters and fighting them and really not paying attention to my posts at all. (And also leaving me way behind - I went to work one day and came back to a page of posts.)

2.) I had a plot that had certain things that needed to happen in the beginning before the main portion of the story, otherwise the story wouldn't make sense. However... I couldn't gently nudge the player into the direction it needed to go, and the RP fell apart.

Now, I know with the second example, I should have been clearer that there were events that needed to be established. I also needed more room for the player/character to make decisions. (Though I did not expect for the character to decide to hole themselves up in their house...) However, the main point of starting the story where I did was to introduce one of the possible love interests/allies before everything in the characters world went to hell in a handbasket.

So here I am, asking you: What makes a good GM? How do you personally GM? How does one GM a fairly linear plot without making the other RPer(s) feel like you are just pulling them along without a choice? How can one GM a roleplay and still be involved as a character? And any other tidbits you might like to share, along with any experiences of GMing or failing to GM.