How to wrap text in LaTeX tables?

Use p{width} for your column specifiers instead of l/r/c.

\begin{tabular}{|p{1cm}|p{3cm}|}
  This text will be wrapped & Some more text \\
\end{tabular}

EDIT: (based on the comments)

\begin{table}[ht]
    \centering
    \begin{tabular}{p{0.35\linewidth} | p{0.6\linewidth}}
      Column 1  & Column2 \\ \hline
      This text will be wrapped & Some more text \\
      Some text here & This text maybe wrapped here if its tooooo long \\
    \end{tabular}
    \caption{Caption}
    \label{tab:my_label}
\end{table}

we get:

https://i.stack.imgur.com/XHn2Z.png

With the regular tabular environment, you want to use the p{width} column type, as marcog indicates. But that forces you to give explicit widths.

Another solution is the tabularx environment:

\usepackage{tabularx}
...
\begin{tabularx}{\linewidth}{ r X }
    right-aligned foo & long long line of blah blah that will wrap when the table fills the column width\\
\end{tabularx}

All X columns get the same width. You can influence this by setting \hsize in the format declaration:

>{\setlength\hsize{.5\hsize}} X >{\setlength\hsize{1.5\hsize}} X

but then all the factors have to sum up to 1, I suppose (I took this from the LaTeX companion). There is also the package tabulary which will adjust column widths to balance row heights. For the details, you can get the documentation for each package with texdoc tabulary (in TeXlive).

Another option is to insert a minipage in each cell where text wrapping is desired, e.g.:

\begin{table}[H]
\begin{tabular}{l}
\begin{minipage}[t]{0.8\columnwidth}%
a very long line a very long line a very long line a very long line
a very long line a very long line a very long line a very long line
a very long line a very long line a very long line %
\end{minipage}\tabularnewline
\end{tabular}
\end{table}

I like the simplicity of tabulary package:

\usepackage{tabulary}
...
\begin{tabulary}{\linewidth}{LCL}
    \hline
    Short sentences      & \#  & Long sentences                                                 \\
    \hline
    This is short.       & 173 & This is much loooooooonger, because there are many more words.  \\
    This is not shorter. & 317 & This is still loooooooonger, because there are many more words. \\
    \hline
\end{tabulary} 

In the example, you arrange the whole width of the table with respect to \textwidth. E.g 0.4 of it. Then the rest is automatically done by the package.

Most of the example is taken from http://en.wikibooks.org/wiki/LaTeX/Tables .

Simple like a piece of CAKE!

You can define a new column type like (L in this case) while maintaining the current alignment (c, r or l):

\documentclass{article}
\usepackage{array}
\newcolumntype{L}{>{\centering\arraybackslash}m{3cm}}

\begin{document}

\begin{table}
    \begin{tabular}{|c|L|L|}
        \hline
        Title 1 & Title 2 & Title 3 \\
        \hline 
        one-liner & multi-line and centered & \multicolumn{1}{m{3cm}|}{multi-line piece of text to show case a multi-line and justified cell}   \\
        \hline
        apple & orange & banana \\
        \hline
        apple & orange & banana \\
        \hline
    \end{tabular}
\end{table}
\end{document}

https://i.stack.imgur.com/pcSlA.png

If you want to wrap your text but maintain alignment then you can wrap that cell in a minipage or varwidth environment (varwidth comes from the varwidth package). Varwidth will be "as wide as it's contents but no wider than X". You can create a custom column type which acts like "p{xx}" but shrinks to fit by using

\newcolumntype{M}[1]{>{\begin{varwidth}[t]{#1}}l<{\end{varwidth}}}

which may require the array package. Then when you use something like \begin{tabular}{llM{2in}} the first two columns we be normal left-aligned and the third column will be normal left aligned but if it gets wider than 2in then the text will be wrapped.

To change the text AB into A \r B in a table cell, put this into the cell position: \makecell{A \\ B}.

Before doing that, you also need to include package makecell.

The new tabularray makes wrapping text in cells easier then ever before.

The package supports all the traditional used column names like c, l, r, etc., but also has its own Q column which accepts various keys to control the width and vertical and horizontal alignment. It also provides an X column, as known from tabularx` which will automatically calculate the width of the column to fit the table into the available text width.

Another nice feature is that all the settings can also be done for individual cells.

\documentclass{article}
\usepackage{tabularray}

\begin{document}

\begin{table}
    \begin{tblr}{|c|Q[2cm,valign=m]|X[j,valign=m]|}
        \hline
        Title 1 & Title 2 & Title 3 \\
        \hline 
        one-liner & multi-line text & multi-line piece of text to show case a multi-line and justified cell   \\
        \hline
        apple & orange & banana \\
        \hline
        \SetCell{h,2cm} wrapping text only in a single cell & orange & banana \\
        \hline
    \end{tblr}
\end{table}
\end{document}

https://i.stack.imgur.com/cxg1E.png

(thanks to Shayan Amani for providing a MWE in their answer!)

\begin{table}
 \caption{ Example of force text wrap}
 \begin{center}
  \begin{tabular}{|c|c|}
   \hline
   cell 1       &   cell 2 \\   \hline
   cell 3                &       cell 4 & & very big line that needs to be wrap. \\ \hline
   cell 5       &   cell 6 \\   \hline
  \end{tabular}
  \label{table:example}
 \end{center}
\end{table}