Swap Magic boot

I bought a flip top lid and swap magic purely to play my 9 month old
Katamari import. Well I'm happily playing Katamari now :-) but the boot
process seems a bit iffy.

Does anyone know if there is a set way to boot up the swap magic disk that
works everytime? Sometimes the PS2 won't read the disk and other times it's
fine, I'm wondering if there is a set button combo I have to perform before
putting the disks in.

Ta.
.