To select alternate columns try the following:

1. Insert a line in row 1
2. Type 1 in B1
3. Select A1:B1 and drag right to the end of the data (so each
alternate column has a value)
4. With this selection press Ctrl+\ followed by Ctrl+0 to hide
alternate columns
5. Delete row 1
6. Select all columns of data and press Alt+;

Now when you copy the selection only the alternating columns will be
pasted.
To restore the original layout, select all cells and press Ctrl+Shift+0
(format column unhide)