The most important feature of a poster is not only its design but its content! If you want to use posters as an effective marketing material or within your business to promote awareness of a product or service to your staff that they need to promote you need good content.
Your customers need to know about your current promotions or product updates to generate business. Make sure if you are trying to raise awareness of these then they need to be the main focus point of your posters. For example, if I have an A0 Poster which is a large format print there is a lot of area to cover on that poster. Usually people will focus on the Title (header) of the poster or to a centre point of the design. In this case your title should contain the key sales point or objective you're trying to emphasize. Same with the central point of the poster, this could contain text or an image that matches the title content. Remember to use colours that blend together and provide a visual appeal to the title and the centre point. These colours don't have to match the title colour it's better for them to be lighter so they appear set back from your most important content. For your centre point to be key to your poster design you need to have symmetry. Ensure that if I have an A1 Poster from top to bottom and from side to side your focus is central. You may want to use your company logo as a central point to your poster design to promote brand awareness and then use the title to promote the current offer or promotion.
A2 Posters are smaller and relatively cheaper then A0 Poster Printing and A1 Poster Printing costs. So take into account size or the ratio of your design when dealing with A2 Poster Printing. Correct proportion must be considered to hit an eye catching title or central aspect of your poster.
Staff within your business will be made aware of current offers or promotions and these should be in their mind to push to consumers to generate venue for your business. The above methods can help them focus on the target niche at that time whether their in the canteen, shop floor, office or reception, push your business intent using posters.