I've done a lot of researching over the last year into passive house heating/cooling.
The best way to cool the heat from windows is to shade them externally. You can do this as simply as using careful planting of deciduous trees and bushes (bare branches mean you'll get winter sun) or through shades and shutters.
As to external shades and shutters, there's a variety of options. Modern sliding shutters, traditional French style (not common in the UK because our windows tend not to be recessed), or contemporary rolling shutters made from either a solar-fabric or wood or metal. They can be solid or meshed, which allows you to see out.
More commonly in this country, and often seen in the Med on flats, are traditional window awnings. You can also install wooden or metal louvered awnings (see photos).
Some of these solutions can be home-crafted with a bit of DIY-savvy or might be more affordable if made with the help of a local joiner.
Internally, I'd look to traditional wooden shutters or blind made from solar / uv-repelling or blackout fabric as you need to block the heat from moving past it. If installing new glass on a side of the house which gets full sun, I'd seriously consider installing glass which prohibits uv light from entering. Basically- sun cream for windows. You can obviously get solar films as well to apply to the glass cheaply.
In very hot countries, people often also hang hang wet sheets or leaves at windows and doors for the air-conditioning effect. For further passive cooling in the home, you need to allow appropriate ventilation. Sash windows are great for this as you can leave an open gap both top and bottom allowing the hot air to escape above and the cooler air to enter below. Opening windows (during the cooler parts of the day obviously) across from each other in the home enables a cross breeze to blow through.
Ceiling fans are also surprisingly effective (as I found last year when I remembered we had an until-then unused one in the conservatory!).
There are lots of diagrams online if you want to look at passive cooling in more detail,they're particularly useful when it comes to knowing how and where to plant trees to shield the home from the sun.
On that note, allowing ivy to grow up walls is also brilliant at insulating the home in winter and keeping it cool in summer.