I carry IWB under an untucked shirt. In the event I can't wear an untucked shirt but am not prohibited from carrying a gun, I pocket carry (chances are if I have to wear a tucked-in shirt I'm also somewhere that prohibits carrying a gun). The biggest drawback is drawing while sitting, which can be awkward at best, or drawing while moving.
Tuckable IWB holsters are an option. I've never used one, though. If I were to use one, I would probably lean towards ones that use velcro to stick to the inside of your belt for a lower profile than clips or loops, but most people probably wouldn't notice or care.
Another option would be a belly band holster worn under a tucked-in shirt. A Kangaroo holster or even a shoulder holster, like one made by Ken Null, worn under the shirt may work, too.
With either option, you should probably pay attention to the color and fabric weight of your shirt as the gun might show through. Others with more experience may be able to chime in on that topic.
You could always use a fanny pack, but that might draw unwanted attention. I use one, but only for jogging.
Some people use Smart Carry, but I don't have any experience with that. It's not a method of carry that interests me. I have concerns about accessibility.
Ankle carry is an option. It can be a good choice if you spend much of your time sitting. Otherwise it can be slow and difficult to draw.
Some people use off-body carry, in a backpack, shoulder bag, purse, notebook, etc., but it's generally not recommended unless you never let it out of your sight and can maintain control of the bag at all times. I don't recommend it unless there's just no other way to carry a gun.
As far as suit-and-coat carry, that only works if you never take off your coat.
