Avoid using pattern fills in charts and graphs
When creating charts in Excel that will be in your poster, try to avoid using a pattern fill. Your patterned striped fill may look fine on your screen (Figure A), but when it is blown up to the full size the pattern will shrink and won't be visible (Figure B).

If you absolutely must use a pattern, there is a workaround you can apply. Double-click your chart in PowerPoint, and press Ctrl + A (to select all) then press Ctrl + C (to copy). This process will put your chart onto the PowerPoint clipboard. Once this is done go to the edit menu and select Paste Special. A dialog box will come up with a selection of different options. You'll want to pick the option "Picture" and press ok. This will convert your Excel chart into dumb objects. (WARNING: You will not be able to edit your chart once it's converted to objects.) Once this is done, position your chart in the poster.  Right click the chart and select the option "Ungroup". After you have done these steps the stripes in your chart will blow up proportionality as seen in Figure A.

Other Suggestions
If you are using Prism GraphPad, please convert your charts to the WMF format, or break them into dumb objects as described above. Otherwise, erroneous  output may occur.

Also avoid displaying two-dimensional data in three-dimensional graphs. 3-D graphs look attractive but obscure true difference among bar heights.

PowerPoint does not allow "wrapping" of text around inserted figures, so if you want this option for a particular section, you need to construct the section as a separate Microsoft Word file (which does allow text to wrap), and then insert this Word file into your PowerPoint poster by the menu command, Insert: Object (select the "create from file" option). When you want to change anything, you merely double-click the section and the Microsoft Word file will be called up, magically, for you to edit.