What is the procedure for preparing petition for wife/spousal visa

Yes, she can move there, marry you, and wait there for your permanent residency (green card) to be completed so the two of you can enter the USA together, with you entering with a green card. You will need to work through the US consulate in Abu Dhabi, Ankara, Frankfurt (family-based applicants only), Vienna (limited), or Naples.

She could also apply for you for a fiance visa and marry you within 90 days of your entry in to the USA. In either event, the processing times will take about a year and may be delayed for security clearance

Given the problems between the governments of US and Iran, any petitions for citizens of Iran to immigrate to the US likely will be thoroughly checked.

It may be likely that your petition will be held up at the security clearance stage.

A few months ago, there was a newspaper story about a young boy (under 10) whose immigration application was held up because his name is similar to that of one of the leaders in the Middle East whom the US government had put on watch lists. Apparently, the boy was not getting security clearance because of the similarity in the names.

Your wife may also wants to be very careful in taking Iranian citizenship as that may affects her US citizenship. She may want to review with an attorney to make sure that whatever she is doing does not affect her US citizenship.

Assuming your wife has some authorization to live in Iran, she could move there, marry you, file the I-130 petition, get the I-130 petition receipt, file the K-3 visa petition, and filing the I-130 and K-3 gives you 2 options to get a visa and immigrate. Currently the processes are very similar in timing but sometimes the name check and security clearances go through faster with one option versus another option.

You will need to have some sensitivity to the affidavit of support issues, as it seems likely you will need a joint sponsor.

Because the I-130 petitions and K-3 petitions are filed with USCIS in the US, and because the case will travel through the US Dept of State's National Visa Center (NVC), also in the US, there is some value-added to having a US-based attorney assist with the case (apart from the usual benefits), because mail will arrive much faster and more reliably to a US-based attorney.

I do agree that a spouse petition in this case would probably go through faster and with less issues than a fiance case, and if you live together while the case is in process, you will be able to document more "bona fides" - that is, more documentation of your life together as a couple, which is always good for the eventual visa interview.