Step 1. First of all, you need to start with a 150 luck item, in base materials, that can be enhanced (i.e. no antique or artifacts).
1.a. There's steps needed to get 150 luck through reforging, that require lower-end runics (mid to high runics don't have the option for luck except as a random roll) See Anon's link above.
1.b. or, you can start with a clean, prized, cursed, or brittle loot piece with 150 luck.
Step 2. Use POF on it to get it to 255, if not already.
Now, is the expensive part. You CANNOT enhance anything over 130-140 luck (varies by crafting skill) successfully without help. 0% success for a smith weapon with JUST LUCK starts at 140; however, changing resists, durability, lower str requirement, or a couple other items ALSO reduce success chance, so any armor is going to have 1 to 6 other properties change, by material (spined leather adds 1 property, gold adds to all 5 resists and lower requirements, and two different woods (3 if you play russian roulette with heartwood's random property that probably won't be luck) come into play for carpenters, with shields using bloodwood for luck, weapons and armor using Oak). So, since Carpentry, Fletching, Tinker, Tailor, and Masonry don't have equivalents to the Ancient Smith Hammer, nor do any of them (other than tailor) go over 100, their point where their breakpoint falls is much lower (as Smith, and presumably Tailor, have a 1% success bonus for each 10 points over GM)
Step 3: You will need the Forged Metal tool from the UO store, bought with sovereigns. You buy sovereigns from EA, then use them in-game in the UO store.
3.a. Set your enhancing tool for the proper enhancing material, and have that material on you in the appropriate amount.
3.b. Use a charge from the Forged Metal Tool (which makes the enhancement chance 100%, instead of the 0% it would otherwise be)
3.c. Enhance the item with your normal tool.
That is how you get a 190 luck item.
Note that there are higher than 150 luck items in archery/fletching (and also throwing weapons). They are two-handed (or for garg stuff, compensating for items without armor type bonuses in the suit) and therefore got an additional luck boost. The rules for enhancing them is still the same.