The following are the requirements for Silver Explore Badge (all must be collected for the achievement):
So close… - Earn a Silver Medal for every drop in 1 Range:
This comes down to preference. Obviously, it's best to head into this using as high a level character as you can, with as high a gear as you can get. I personally did this on the Rockies range, but whichever range you're most comfortable with is best. Alaska is a popular one for this as well.
Estate Tax - Earn a total of 15,000 SSX Credits from ghost wins
First, you'll want to complete some runs on any track, in Explore mode. After you've done that, this will come with time. If you don't have anyone on your friends list with the game, visit the forums on this site, or any other achievement sites and add as many people as you can to speed this up. With quite a few people on your friends list, eventually your records will hold up against their challenges, and you'll earn enough credits for this badge requirement. You can also boost this, however it'll take a little bit longer. Just set a time on a track in Explore mode, and have your friend lose to that ghost over and over. You'll only be allowed to bank your ghost wins after the "While you were away" screen when you first boot up SSX.
Ghosts Everywhere! - Your records have withstood 25 challenges from your Friends
Same as Estate Tax. Set some records in Explore mode, and have your friends lose to them. Alternatively, just add as many people who play SSX to your friends list, and this will come with time.
Are We Still Friends? - Beat 25 Friend's records
Same as Estate Tax, except you'll be beating the ghosts instead. Have your friends set low times on some tracks in Explore mode, then go beat them if you'd like to boost this.
Stash - Place 5 Geotags that never get collected (earning you the max):
This can be somewhat tricky, but will come with time by just placing tons and tons of geotags all over the mountains. I would suggest getting your character up to level 7, as you can then have 2 geotags in inventory per race. Then, either put them in low traffic areas such as right before you die or behind trees, etc. Alternatively you can use a wingsuit and fly to crazy places and put geotags there. They will expire after 24 hours real time, and you will be able to bank the winnings after the "While you were away" screen. Go with quantity for this one, just place as many as you can stand to place, always go into races with Geotags equipped, and you'll get this eventually.