Successful Sneaking isn't just a question of physical control, but of being on the alert for potential sources of sound, such as creaky floorboards or dry twigs on the ground, and of recognizing and avoiding these in good time. A Sneak Test can be countered with a successful Perception Test. A sneaking party is only as proficient as the group member with the lowest Talent Prowess value.
As the group member with the lowest Sneak value determines the results of the Test - so the loud and noise dwarf instead of the quiet and proficient elf - it can be smart to place your party just out of sight of the target, then select only the one character who is best at sneaking, and let him/her do the job. Make sure the distance from the rest of the party is not too large, though, or the rest of the party will automatically come running after him/her. It is also worth knowing that summoned animals will attack enemies in sight even when you are sneaking.