Here are some tips on how you can minimize risk of getting your pokemon sniped / lost in gts.
You can still deposit whatever you want, these are just some personal recommendations:
- no fossils
 
- no starters
 
- no eevee or any 12.5% gender ratio mons
 
- no early route pokemon
 
- no pokemon below level 11
 
- put a lvl. restriction
 
- specify the exact level and gender of your deposited pokemon in your post
 
- avoid messages like "thanks", "thx", "thank you" cause I might miss those
 
- recommended messages (easily identifyable): "Theorymon", "Theorymon!!!!!", "Theorymon rocks!" "Theorymoon", "lego", "most", "cannibal"