Q: How do I go about getting Magic Find?
A: The easiest and cheapest way is to buy/make magic find food.
Omnomberry Bar Is currently my favorite food to use. Another option is Chocolate Omnomberry Cream as it provides 40% magic find but it is only while you have a boon and it also does not provide increased gold gain so it is inferior for farming.
A more expensive but permanent way to get magic find is through equipment and upgrades.
To my knowledge there are 4 Runes that provide magic find, and 1 Sigil that provides magic find: (Please note that an effective way to get more magic find is to stack 5 of one type and 1 of another, giving 60% rather than 50% magic find.)
Magic find armor is most easily obtained by having it crafted or buying it, note that the former is cheaper and you need only ask the crafter for the mats. Note that weapons are made from similar materials and called by the same prefixes.
The prefix is "Explorer's", providing Magic Find, Power, and Precision, and they require a tier of the claw fine crafting material depending on your level in addition to other materials. You can have it made in whatever rarity your budget allows, at level 80 you could probably obtain a entire Masterwork set for under a gold if you buy the materials yourself and get a friend to make it for you/make it yourself. The exotic set is considerably more expensive as it requires 5 ecto a piece in addition to the highier tier materials.
If that isn't your speed you could look for armor with the prefix "Traveler's" as that provides Condition Damage, Power, and Magic Find.
For Rings/Accessories/Necklaces you are looking for items with the prefix "Opal" and it also provides Magic Find/Power/Precision. Once again buy the set that fits your budget as the difference in stats between rarities is small.
Q: How does Magic Find work?
A: Magic find increases the chance you obtain highier rarity items. It works on getting crafting materials. It works on getting Blues(Fine)/Greens(Masterwork)/Yellows(Rare) from mobs.
It is believed that all your bonuses to the stats are added up and that modifies the drop tables. So if you have 2 bonuses of 50% magic find for example you would end up with 100% magic find. So if a mob had a 5% to drop a 'fine' quality crafting ingredient or piece of equipment that chance would be doubled to 10%. I must caution that this is not fact and still being tested, because current smaller tests seem to indicate that magic find is actually more effective that what is described above as this small sample seems to indicate:
Level 40~ skales.
50 kill sample - 0% MF - 6/50 dropped bloods.
50 kill sample - 20% MF - 11/50 dropped bloods.
50 kill sample - 63% MF - 21/50 dropped bloods.
Data from Shantarr.
Q: Is it worth it?
A: If you plan on killing things yes, a thousand times yes. Even spending gold on theOmnomberry Bar just to go out and farm for for a while is extremely worth it. You'll easily make back and probably even double/triple the 1-5 silver the food cost you just through the 40% increased gold alone. The 30% magic find is a massive boost for something that is already effectively free at worst and otherwise makes you money.