Okay, for the moon sigil, you have to defeat all of Belgemine's aeons in Remien temple (however, in order to defeat them all, you have to have attained them all!). For the moon crest, go to Besaid island beach (where you first get washed up) and go to a south eastern cove where you'll find a chest with it inside. That's Yuna sorted out.
The venus sigil: this is a tricky one, you have to dodge at least 200 lightning strikes consecutively in the thunder plains in order to get this as a reward at Rins travel agency. The crest can be found on the Farplane in Guadosalam (after you've defeated Yunalesca). That be Lulu.
The saturn sigil and crest are Kimahri's babies; for the sigil, you have to complete both butterfly hunts in Maclania woods (after you've defeated Yunalesca). The crest is on Mt. Gagazet, just after you've defeated Seymourflux you'll find a chest further along the path, therein lies the prize.
For the mercury sigil, you have to complete the time consuming cactaur hunt game in Sanubia desert. Press 'square' at the cactuar stone in West Sanubia (below the sandstorm) to start the hunt. You do not have to catch all ten cactaurs in order to receive the sigil, just take whichever sphere you receive back to the stone, when you have ten sphere's you will gain access to the cactuar valley, the sigil is in a chest there. The crest is also attainable in West Sanubia on the west side half way up, in a chest. Happy Rikku?!?
Okay, the Mars goodies. For the Sigil, you have to have 'captured' at least one of each beastie in any ten of the areas of Spira and return them to the monster arena, you will get the sigil as a prize. The crest is at the very end of the Mi'hen oldroad (if you cann't be bothered to walk, rent a choco). Go get 'em Auron.....
And finally, Jupiter.......ah well; I hope you have been keeping up with your blitzball. The sigil will only appear as a league first prize after you have attained all of Wakka's overdrives. The crest is in the right-hand locker room in Luca stadium in one of the lockers. Wakka, sit down.......
Well that should keep ya going for a while. You didn't mention the Sun crest and sigil for Tidus so I'm presumning you're okay with them. If not, let me know. Laters.....