How do i change the x and y steps of an plot?

edit

The documentation of plotting options is indeed cumbersome and hard to track. As you can see in the doc of the plot function:

sage: plot?

You can read:

 * For the other keyword options that the "plot" function can
   take, refer to the method "show()" and the further options
   below.

So, you can access to more options by doing:

sage: p = plot(-1/2*x+1,(x,-2, 8), rgbcolor=('#00c147'))
sage: p.show?

Then you will read how to use a ticks option, so that at the end, you can do something like:

sage: plot(-1/2*x+1,(x,-2, 8), rgbcolor=('#00c147'), ticks=(range(-2,9),range(-3,3)))

There are many more options. In particular, you can see how to pass most matplotlib tricks to tune your plot.