The [H] float option turns the float (figure, table, etc.) effectively into a non-float (although it may have a regular caption) making it appear in the final document where it was put in the LaTeX source. This can then result in much extraneous white space (what happens if the [H] float requires 3 inches vertical space but there is only 2 inches available on the page?).
If you really want a float to be a non-float then don't call it as a float e.g.,
%%% begin{table}% don't use this!
\begin{tabular}
% tabular code
If you need a caption then you can use the caption
package. For example
\usepackage{caption}
% etc
\begin{center} % if you want the tabular centered
\begin{tabular}
% etc
\captionof{table}[LoT entry]{Nonfloating table caption}
\label{tab:X}
\end{tabular}
\end{center}
% etc
LaTeX tries very hard to position floats in a pleasing way via the optional float parameters [htbp]
. If you think that you can do better then good luck to you.
A comprehensive discussion about floats and what you can do with them is in the 43 page Chapter 6 of Frank Mittelbach and Michael Goossens The LaTeX Companion, Second Edition, Addison Wesley, 2004 (I understand that a Third Edition may be in the offing at some future point). The chapter includes details of how you can adjust the allowable spaces for top (t
), bottom (b
) and here (h
) floats.
The memoir
manual (>texdoc memoir
) has a Chapter Floats and captions that contains similar information. The Not so Short Introduction to LaTeX2e (> texdoc lshort
) also has useful information on the topic.
Following from jfbu's comment I should have remembered that Frank Mittelbach wrote a comprehensive article How to influence the position of float environments like figure and table in LaTeX? It can be accessed, and printed from, [TUGboat, the journal of the TeX User Group]{https://tug.org/TUGboat/tb35-3/tb111mitt-float.pdf}