As "pretty" is a subjetive term, first think in the type of publication: in formal documents always use as few as possible horizontal rules using booktabs
, avoid vertical lines and ... that is all (in many cases).
In some cases, some additional vertical and horizontal padding can be controlled with \arraystretch
and \tabcolsep
, respectively.
For non so serious publications... well, there are many possibilities to make "pretty" tables, where you can even use the evil vertical rules, dashed or dotted lines,, add backgrounds, color, exagerated paddings or even use a non tabular environment to cause some visual effect. Of course you can mix these options in endless combinations to make it even more jazzy/striking/flaboyant/gaudy. Be imaginative. Some examples:

\documentclass[]{article}
\usepackage{fancybox, tcolorbox, xcolor, booktabs}
\parskip2em
\begin{document}
\centering
\begin{tabular}{p{2cm}cccccc}
\toprule
Question\dotfill & 1 & 2 & 3 & 4 & 5\\
Marks\dotfill & $x$ & $x$ & $x$ & $y$ & $z$ \\
\bottomrule
\end{tabular}
\[
\left[\begin{array}{cccccc}
\mathrm{Questions} & 1 & 2 & 3 & 4 & 5\\\specialrule{.1em}{.3em}{.3em}
\mathrm{Marks} & x & x & x & y & x
\end{array}\right]\]
\ovalbox{\sffamily
\tabcolsep1.5em % horizonal padding
\begin{tabular}{l|ccccc}
Questions & 1 & 2 & 3 & 4 & 5\\[.5ex]
Marks & x & x & x & y & x
\end{tabular}
}
\tcbox[left=0mm,right=0mm,top=0mm,bottom=0mm,boxsep=0mm,
toptitle=0.5mm,bottomtitle=0.5mm,colback=blue!05,
title filled, title = ~ My table ]{%
\renewcommand{\arraystretch}{2}% verticall padding
\begin{tabular}{l|ccccc}
Questions & 1 & 2 & 3 & 4 & 5\\\hline
Marks & x & x & x & y & x
\end{tabular}
}
\end{document}