I also use the "single-celled table with title" method for inserting
graphics with captions, but since you mentioned both figures and tables, I
want to add a suggestion to the good advice others have given.
Consider using a single numbering system for all graphics. It greatly
simplifies things. A reference to "see table 7" doesn't tell you where to
look for it. Table 7 might fall before Figure 1, for example. It's
unintuitive and confusing. If a cross-reference says to see Table 7 and that
table is several chapters away, it becomes very difficult to find. Having
all the graphics numbered in a single series makes life easier for the
reader. Figure 7 is always after Figure 6 and before Figure 8.
Here's a link to a short article about an IBM study that concluded it is
best to simply call everything a figure and number it in a single series: