1. Read the many many posts and advice given by others on this site. The posts are authentic and real, not fake one-sided articles that you might find on other websites. 

2. Start the trend in your family that you guys will always be open with what you need and with your feelings. If you can’t express how you feel or if you can’t ask for something you will start to resent the child and your wife 

3. Tell your wife that the marriage comes first and then you and she together will prioritize the child’s needs.  A child needs to see that parents are in a decent relationship, and that parents are a strong unit. 

4. You must be able to maintain your authority in the household but do not think that you will automatically become the parent to this child. You are another adult in the household. You deserve to be respected but don’t expect to be loved or treated as though you were a parent.

5. Don’t start out by going out of your way to provide fun or anything else for the child. The child won’t appreciate it and you’ll just feel used and marginalized. 

6. Don’t change your lifestyle just because skid is there. Continue your daily routine and skid will have to adjust to you, not the other way around.

7. Establish quickly that the house is yours, not skids.

If you haven't already discussed how to handle the ugly things, do it now -- before it happens. When you negotiate the terms ahead of time, there may be less friction when you actually have to apply them. Think of it like a business deal or a contract so everyone knows how things will be handled...such as:

If she's not there and SS misbehaves, will you handle it or will it wait until she gets home? Is she open to you being an authority figure or doling out discipline when she's not there or even when she is?

If SS starts rejects you ("you're not my REAL dad!") how will your wife handle it? What if he back talks you or disregards you when you tell him "no?" What is your TEAM plan to handle this kid?

Will you be expected to drive him to activities or doctor's appointments or will she handle all his care?

If your wife lacks boundaries with him (lets him sleep in your bed, lets him eat junk all day, buys him toys because he whines) is she open to you helping her set boundaries or will she side with him against you? (This is when parents love to throw our child-free status in our faces.)

Basic rules: Will he have a bedtime? Will he have chores? Will you have time set aside just for you and your wife?

There's no replacement for preparedness. It's really important you and she are on the same page and present a unified front to this kid, because if there are problems, the kid will sense this and maximize them to his benefit -- that's just how kids are. You don't want to fight about how to handle situations in front of the kid because once they sniff that crack between you, they instinctively leverage it into the Grand Canyon.

Don't be shy about asking frank questions like those above -- it need not be confrontational. Tell her you don't want to overstep, but you want to do what you both feel comfortable with you doing, so now's the time to figure out what that is. You are setting the tone of your family dynamic now that will dictate the tone for your marriage and you only get to present it as the standard to the kid once -- on the first visit. Negotiating the terms with your wife will show her you take this seriously and  want guidance on where you fit into the parenting her kid because you're all family now! Also, by discussing this stuff ahead of time, you put her on notice that the expectation is she will follow what you negotiate now. If it hits the fan, you can remind her what you both agreed in the honeymoon phase of this kid's presence (the start of the first ever visit).

Good luck! I hope we never see you on StepTalk again because it's going so swimmingly!