Justify your text & ensure that lines don't break in the middle of words.
Use a standard, simple font such as Times New Roman, Calibri, or Arial.
Use large font & make section headings bold and/or a bit larger.
Dark text on light background is best. It is easiest to read and uses less ink when printing.
There are various PowerPoint templates available online for poster presentations, including the first few at this Microsoft link. If you use a template you find online from another person or institution, include a small note about the template source.
There should be logical flow between sections. A standard arrangement is columns followed top to bottom and left to right.