In Macbeth, how does Shakespeare present Macbeth in Act One?

Banquo: Worthy Macbeth, we stay upon your leisure.

King Duncan compliments Macbeth over and over on his defeat of Macdonwald; this is how much King Duncan respects and trusts Macbeth:

Scene IV

Duncan: O worthiest cousin!
The sin of my ingratitude even now
Was heavy on me: thou art so far before
That swiftest wing of recompense is slow
To overtake thee. Would thou hadst less deserved,
That the proportion both of thanks and payment
Might have been mine! only I have left to say,
More is thy due than more than all can pay.

Macbeth’s response is to shrug it off, to act as if it were just natural for any man to do as he had, and therefore, acknowledge that no compliments are necessary. This shows Macbeth as a modest and humble man.

Things begin to change after King Duncan announces while visiting Macbeth’s castle that his own son Malcolm will become the next heir to the throne. This means, that if Macbeth is to be king, he will now have to wait until not only Duncan's reign, but also Malcolm’s reign to end. Macbeth is not likely to be alive by that time, and if he is, he’ll be much older. He begins to wrestle with his thoughts between remaining loyal and committing murder. His greed for the throne and all it offers is beginning to get the best of Macbeth:

SceneVII

Macbeth: If it were done when 'tis done, then 'twere well

It were done quickly: if the assassination

Could trammel up the consequence, and catch

With his surcease success; 

He's here in double trust;

First, as I am his kinsman and his subject,

Strong both against the deed; then, as his host,

Who should against his murderer shut the door,

Not bear the knife myself.

He appears to have decided to remain loyal to the king. When Lady Macbeth questions him, his response is:

Macbeth: We will proceed no further in this business:

Unfortunately, because of a festering greed and his wife's talking down to him, Macbeth’s resolve begins to crumble, his greed gets the better of him, and he comes to a decision:

Macbeth: I am settled, and bend up        

Each corporal agent to this terrible feat.

Away, and mock the time with fairest show:

False face must hide what the false heart doth know.

Though Macbeth has not taken any criminal actions by the end of Act I, we can see how quickly his persona and his thoughts have changed in such a short time and how easily influenced he was by his status and people around him. Though his friends still see him as valiant and worthy, Macbeth has begun to act anything but.