What are the practices to naming organic chemicals by abbreviations?
The only accepted practice without any further constraints is to only use element symbols and sum or constitution formulae. Taking your and a few other examples, that would result in:


$\ce{C2H5OH}$ or $\ce{H3CCH2OH}$
$\ce{C6H5COCH3}$
$\ce{H3C(C6H5)2COH}$
$\ce{H3CCOOC2H5}$
$\ce{(CH3)3COCH3}$


The more complicated these get the less clear everything is. Thus, many people make use of a set of common abbreviations. However, these must be defined in a list of abbreviations, footnotes or wherever.


$\ce{EtOH}$
$\ce{PhAc}$[1]
$\ce{MePh2COH}$
$\ce{EtOAc}$
$\ce{$t$BuOMe}$


Where the symbols $\ce{Et, Ph, Ac, Me, $t$Bu}$ would need to be defined to mean ethyl, phenyl, acetyl, methyl and tert-butyl, respectively.

Finally, of course, you can suggest other common or your own abbreviations and use them (consistently!). For example, in my group it is rather common to abbreviate $\ce{EtOAc}$ as $\ce{EE}$ (because of its retained German name Essigester). Or a common way to denote the last compound in that list is $\ce{MTBE}$ or $\ce{TBME}$ (methyl-tert-butylether or tert-butylmethylether). Again, these abbreviations must be defined in footnotes or a list of abbreviations in best practice.

Finally note that an abbrevation typically includes all the hydrogens. Thus, methyl is always $\ce{CH3}$; $\ce{MeCl}$ is permissable for chloromethane but $\ce{MeCl2}$ does not mean dichloromethane. Consequently, neither $\ce{EtPh2OH}$ nor $\ce{Ph2EtOH}$ are permissable for 1,1-diphenylethanol, since carbon $\ce{C{1}}$ has no remaining hydrogens (not 2 as $\ce{CH3CH2}$ — ethyl — would imply).



[1]: Note that $\ce{Ac}$ can also mean actinium. If your paper uses actinium anywhere, do not use $\ce{Ac}$ as an abbreviation for acetyl or it shall cause confusion. The same is true for $\ce{Pr}$ and praseodymium and a few even less common others.