Chest measurement- First and foremost thing that you have to keep in mind is that you should not wear any bulky item while doing measurement. Measure the portion around beneath your underarms. Always insert a finger between tape and chest to get a perfect fit.
Height measurement-for this you should take measurement from head to toe keep in mind that you should not wear shoes while taking measurement.
Length of coat Short 5'8'' or less Regular 5'9'' to 6' Long 6' to 6'3'' x-long 6'4 or above
For sleeve-keep your arms down in straight form and now take the measurement from centre of your neck from back side to one inch more towards your wrist for a comfortable fit.
For neck-measure at the collar level around the neck again keep a figure between tape and your neck for a proper fit.
For waist- remove your belt and sweater if any first of all and then from the level of navel around your natural waist tap around slightly in snagging manner for proper fit. Seam measurement-for this place the tape down the side of leg all around towards the floor other side of tape must be on the right hip at waist band.
For more details you can follow charts given in terms of above measurements at mensUS. This chart may be referred as the thumb rule type of chart. The ranges given on the right side are the to be used approximately. Though it also depends on you build. But people will commonly fall in the range. So you can go with the chart without giving a second thinking.
An important thing which should be kept in mind is about your pocket. Well, here we are not talking about the expense on your tuxedo but the pockets you are going to have in your tuxedo.
For customizing your signature tuxedo you can also mention pocket size also. Occasion must be keep in mind for sure as choice of the notch lapels is obviously also important as dinner jacket will never have notch lapels. They are not much formal for a tuxedo. Peak type of lapels and shawl type of collars are the only acceptable options, whether single or double breasted.