What is the best way for a guy to wear a smart phone, keys and a wallet?

I put my wallet in my back pocket. That opens up the left and right pockets for my phone and my keys.
I also always carry around a backpack on my back with other things. If you carry a backpack, you can put any of the three things in there. If a backpack is too much, you could try one of these things (lady not included).

I’m an atypical girl – I hate carrying a purse.
Smartphone with a case that holds my driver’s license and credit card in my left front pocket;
Cash in the right front pocket and lip balm in the coin pocket;
Keys attached to the belt loop with a carabiner, then tucked into the front right pocket so as not to jingle.
Receipts go in the back pockets or immediately in the trash.

I have one pair of cargo pants – the extra side pockets are nice. Guy’s pants and jeans have deeper pockets too – some of my pants barely fit my iPhone 5s, and that’s a fairly small phone compared to some that are out there.

Cell phone in left pocket, wallet in back pocket, and keys in right pocket. Go with the minimum number of keys you can. If possible get a thinner wallet or empty the useless stuff out of it.

Say good bye to bulky pockets and say hello to style and storage with a satchel.

Tool belt.

Bigger pants… The cellphone on a clip needs to go so you need bigger pockets or a smaller phone. My iPhone isn’t noticeable in my front right pocket.

I like @johnpowell‘s answer : “Bigger pants”
I have phone and keys and loose cash on the left, wallet and blues harp on the right.

If you are anywhere there might be pickpockets you never want to put anything valuable in your back pockets especially a wallet. Also unless your wallet is unusually thin, sitting on it will put your hips on uneven level and can cause various posture related problems like sore back.

I don’t worry about fashion much beyond cleanliness and basic coordination of color/pattern. I lean much further toward practical. Some women will find that unattractive. Other women will understand that a practical guy is better to have around on a regular basis and especially when it really counts. Your mileage may vary.

Carry a manbag.

Okay, I still like the toolbelt idea, but that’s just me. I like guys wearing toolbelts.
I’m a woman, and I used to carry a purse, but then a thing happened to my life. I had to use crutches for a long time, until it got too hard, and I had to go with a chair.
Carrying a purse is just awful when you are trying to get arouhd on crutches. I was left with trying a variety of ideas to carry my stuff. Fanny pack didn’t work well, it would slide around my waist and block motion of the crutch, down I go. Some of my pants, shorts, skirts, I sewed in a small front pocket, sort of like some men’s swim trunks have. My favorite alternative is vest, jacket, or coat with an inside breast pocket. Both reduced the amount of clutter in my regular pants pockets. Both keep things less available to pick pockets. Sometimes I have worn suspenders, and clipped my phone case onto them.

@Jonesn4burgers Good point about a vest/jacket with copious inside pockets.

A friend came back from a middle east trip with a great vest into which he could securely put everything he carried. The traditional outfit that goes with this vest (for hot desert weather) has lightweight pants with no pockets and a light-weight long-sleeve shirt.