It used to be that grooms had only four things to worry about: 1. Getting the right engagement ring; 2. Planning the honeymoon; 3. Paying for the rehearsal dinner; 4. Showing up on the big day reasonably sober.

Well, things have changed, at least according to a new book, "The Groom's Guide: For Men on the Verge of Marriage."

Back in the day, if a man getting married had wanted to be involved in the planning, he would have been scoffed at. The bride and her family carried most of the weight (but the wise would-be groom still kept his checkbook handy, just in case). These days, clearly, are more complicated.

"You can do this," the book declares. "But you have to know the ropes before you tie the knot."

The Black Tux, the rental tuxedo and suit company, produced this book, so there's a lot of advice about how to get dressed for the big day. But there are a lot of other things to consider in the book, which is written with a stylish wit reminiscent of those old party manuals published by Esquire magazine.

Here are the essentials from "The Groom's Guide" that every groom should consider.

• Do your research. Even though the opening lines of the book say to "ignore anyone who tells you there are rules you must follow," clearly you want to do the right thing. So if there's something that isn't clear, ask questions of the officiant, caterer, band or DJ, florist, reception hall manager — everyone.

• Keep pen and paper handy. Write out your vows beforehand, so you can read them. Jot down a list of people you need to thank at the wedding, and keep it in your pocket to remind you. Compose a "thoughtful note" to your partner, and have one of your groomsmen deliver it.

• Have an open bar. That doesn't mean it has to turn into a pricey free-for-all. Include two or three pre-mixed drinks that guests can serve themselves and perhaps a keg of beer with a tap.

• Buy shoes. "Options to wear with suits are pretty much endless — oxfords, slippers, loafers — but tuxedos are traditionally worn with black patent oxfords," the book notes. "Again, rules are (sometimes) meant to be broken, and today's men are branching out more with their footwear, even if they opt for a tuxedo." But the book offers a caveat: "Please don't wear a tuxedo with flip-flops."

• Travel strategically. If you're going to be flying to the wedding location, pack the "important suit" in your carry-on. (The book shows how to do it.)

• Find the "day-of-Zen." Don't let the minutiae or the moment(s) get to you before, during or after the wedding. Relax, stay calm, focus.

• Keep focused on your partner. Maybe you haven't seen a couple of those friends for years, but your wedding day is not the time for a lengthy reunion. Call them later.