When I used oak chips, I would simply boil some water (in a tea kettle) and pour that over the amount of chips I was going to use. I would have already sanitized the jar, and would put the lid on the boiling water (with the chips in there)... I then let it cool to room temp before pitching it all in... Even 3/4oz can be very noticeable in a brew.
For when to add them, wait until it's otherwise ready to keg before adding the oak. Then give a taste test after about 2 weeks and decide if it needs more time or not. I went 4 and 5-1/2 weeks in two different brews with oak chips... I've also used 1.5oz oak cubes in another brew (a wee heavy) which sat on them for just over a month.
Depending on the toast level, you'll get different things from the oak... I've been using medium toast so far. The chips are/were French, but the cubes are Hungarian. That also impacts what you get from the oak.
You can add the oak in primary, if you want, or rack to another vessel. More of a personal preference/choice than anything else. So far, I have racked before adding oak, just to make sure I had less things competing with the wood for flavor and such. But, I also let brews sit on the yeast for 4-8 weeks before doing any racking.
Make sure the brew is otherwise finished before you add the oak. If you wouldn't otherwise bottle/keg the batch, don't add the oak. Depending on how much you want, from the oak, will determine how long you leave them in... One thing to keep in mind, chips are more one dimensional for flavor. Where cubes are much more rounded. Spirals and staves are even closer to using actual barrels. Also remember that what the oak gives the brew will change over time. I've had this happen with the old ale I added oak to. It started off as having this nice smokey wood type flavor to it. After about two months in bottles, that has changed to a more vanilla flavor.