Casual shoes these days seem to be split into a few distinctive styles, there are the standard trainers, slip on flat shoes, high back trainers and thick design skate or street sports shoes.
The standard trainer is commonly associated with big sports brands such as Adidas and Nike, it is commonly perceived to be 'tacky' to wear these kinds of shoes with the smarter casual where available these days but their primary use endures as sports equipment. If worn with the right set of clothes anyone can pull trainers off but make sure you don't go with a smart pair of jeans and a shirt cardigan combo.
Pumps or slip on shoes have become increasingly popular in the last three years, they were launched forward by alternative clothing brands such as Vans to target a unisex market (although extreme designs or colours often corner some styles for a gender). They go well with either a casual or smart casual style and come in a massive range of colours and patterns. Their popularity has recently grown even further with many mainstream brands taking the style on (especially for women) and making slightly more elegant versions of what originally existed.
The high back trainer's style is most commonly associated with the Converse or Converse Classics shoe design. These shoes tend to be made of a canvas material which is comfy and breathable and tends to lend itself to plainer designs. They are often available in a selection of neutral colours meaning they can fit in with many outfits. Their plain design also lends them to a smart feel however they can still appear very 'trainerish' if you are planning a smart-casual look.
The thick designed trainers more commonly known as skate shows are more much more widely than they were 5 years ago. They are strongly associated with the skate and rock scenes and the Vans brand. They feature robust styling and high durability and go well with a more casual look. They look very much like standard trainers but styled to be much flatter and wider.
These days t-shirts can say a lot about a person, mainly because there are so many different styles available therefore selecting one to where must mean you have an affiliation with what is printed on it.
There is really two distinct T-Shirt styles out there at the moment, branded t-shirts tagged with either a company or product logo and 'retro' or 'vintage' style t-shirts tagged with products and images from past fashions. Branded t-shirts usually appear a little smarter than their retro counterparts and are also more standardised colours (such as blue, black and white). The retro styled shirts usually feature a logo or picture of an out of date TV show or company and are often made to look faded and old on purpose. They can also feature puns and made up but funny companies based on real life older brands. They are much less formal than standard t-shirts.
Hopefully this article has given you an idea of what styles are available for you to combine as well as the basic principles regarding what the styles actually are. You can visit a multitude of good stores for more information and pictures of the clothing items that you can potentially purchase including brands such as Original Penguin, Vans and Crocs.