To complete this Achievement you must obtain at least (only has to be one) Gold Medal in all applicable Hobbies and Pastimes. This can be completed with any of the characters earning the Gold.
This includes:
* Triathlon.
* Street Race - Win a Street Race (There is also a mission where this can be done, Called 'Shift Work' under the Strangers and Freaks tab with a 100% Gold Completion, I do not believe winning is enough, you DO NOT have to gold medal this specific race to obtain the achievement as when you win this race even without 100% completion, more are unlocked). Show up Between 22:00 - 3:00
Thanks 'Its Lowey'.
* Off-road Race. (Possibly both a Moto/Atv AND a truck race)
* Water Race - Show up after a story mission, can't miss it.
* Flight School.
* Gun Range (at ammunation).
** SnelleSjonnie pointed out that the gun range has many different gun categories with gold medals in each of them, in regards to this achievement I would assume that you only need ONE gold overall but to be safe I would get one from each gun category.
***Update*** Carlillo92 said they had only done the pistols category, so it seems as if you only need one gold medal from any of the categories.
*Note* - I had not done either Tennis or Golf when I unlocked this so they are not required. II ClasseY II has confirmed you do NOT have to play darts either.
If I have forgotten any feel free to comment and I will update it