Here are a few methods that will crate a 'shiny' finish, combine them as you wish to achieve desired reflectivity. Since buffing/polishing can be tough work, ensure your mold and concrete are acceptable before you start, this will minimize the time spent polishing.Mold:The less imperfections here the better you finished piece will look. Try to use a mold with a smooth surface and with no debris.Concrete (type):There are quite a few varieties, and they will all have their pros and cons. If you are looking for something ornamental and strength isn't really an issue, then try to look for concrete with small or little aggregate. They do make 'tinner' concrete which you can buy commercially, though a bit more expensive the results are amazing.Polish:This is the end process. When you have done all you can with teh above 2 steps you must turn to polishing. This is labour and time intensive. Use the correct grains from course to fine just like when working with wood. When you've got it really really smooth and awesome, slap on some sealer to keep your work looking new. Good luck!