Q1. How to prepare the paper using journal sample?
A1. Please, visit our sample page.

Q2. The font and size of theorems, lemmas, propositions?
A2. The size is normal, i.e. the same as in the whole text. The font of words theorems, lemmas, propositions must be bold. The font of body must me slanted.

Q3. The font and size of definitions, remarks, notes?
A3. The size is normal, i.e. the same as in the whole text. The font of words definitions, remarks, notes must be bold. The font of body must be romman.

Q4. I have figures in the paper. What format do you accept?
A4. Preferably: PostScript (ps) and Encapsulated PostScript (eps).

Q5. How to include ps or eps file in latex code?
A5. In order to include the PostScript files generated, it is necessary to include graphicx package:

\usepackage{graphicx}
in the preamble of the latex file.

The code to include file is:
\begin{figure}[t!]
\center[scale=1]{figure_name.ps}
\caption{Caption of the figure}
\end{figure}

Q6. What about the tables?
A6. The latex code is similar:
\begin{table}[t!]
\begin{tabular}{cc}
11 & 12\\
21 & 22
\end{tabular}
\caption{Caption of the table}
\end{table}
Remark. The xcolor package provides support for coloring table rows (columns, cells, etc.) in a variety of patterns (The colortbl can color rows, columns, cells and rules, too).
There is a useful article by Lapo Filippo Mori in the PracTeX Journal that describes the usage of both packages.

Q7. I notice that the space between each column of a table in LaTeX is not quite wide. Is there any way to set this?
A7. The parameter to act on is \tabcolsep, whose value is usually 6pt. So,

\setlength{\tabcolsep}{12pt}
will double the intercolumn space. \arraystretch defines vertical spacing of tables:
\renewcommand{\arraystretch}{1}
This command serves as a multiplier for the row height.