There is no secret. Always use acidic products. Period. Alkaline products lift the cuticle, leaving the hair shaft jagged, hence, less light reflected. If you are blonde, you will never appear to have as shiny a mane of hair as someone who has dark hair...it's how the eye percieves the light reflected and absorbed.
Also, some heads only grow hair shafts with cuticles slightly askew. Some people can have sheen, instead of shine (those with natural kinks and little curls). If you have fine hair, it will be more difficult for it to shine unless slightly oiled. Coarse (thick) haired people have a much easier time with that. If you rinse the conditioner off with cold water instead of warm, the hair will be shinier. Likewise, if you use the cool blast to quickly graze your hair after you've used the hot air on your hair dryer, your hair will shine... that's the only reason why someone invented that little blue/grey trigger on it.
You can cheat and use a silicon hair gloss too. I think "IC" makes some good ones. Stay away from the products that are alcohol-based, it will kill any chance you had of having the shiniest hair that day. But hair with too much product might shine at first, and become dull very quickly because air particulates like to stick to it, especially if it is pertroleum based.