How to align vertices with other vertices I'd like to select a vertex, then select several other vertices and make them somehow aligned with the first one by e.g. Z axis.

Here is example picture of what I have - the highlighted vertices are ones which I'd like to align.



If possible can someone explain me how to do it. 
If it is not, could you provide a good alternative.
The best way is to select the vertices that you want to be aligned. Then press s to scale, press z to constrain to the z-axis. Then type zero and press enter. Then all of the vertices will be "flat" or aligned along the z-axis.