For the July one:

Always go first.

Assuming the table is symmetrical around only one point, the centre of the table, place the first coin on that point.

Every move after that place your coin in the location directly opposite the last coin played, the mirrored location around the point of symmetry.

Since you are always playing a symmetrical position, you know that there will always be a space available for you after the previous coin was played.

[edit] looks like the answer on the site is almost the exact wording as mine :)