2 year old stud

Question
he is a reg golden retriever and this will be his first mating she humps him but the does not try and mount her, she sstarted her heat on monday well thats when i noticed her old blood kind of a brownish color, that time she was in heat she went to a studs home they clame she did mate 2 times but never got pregnet but had  had a litter before ,so any how even though this is his first time will he know when the time is right to mate will he know what to do when should they mate what day ? if we noticed the brownesh blood monday march 23rd and now its finally red as of the 24th so what do should i expect them to mate so i can watch and be there to asure all is safe? and will he get it? its sad cause the person i bought him from kepted him locked in a cage out side for his life but he has ajusted perfectly to our home but had never been with people kids or other dogs but is doing so well just rusty so please let me know ,he is such a smart golden long hair show bloodline i hope he will get it just wnat to know every thing i asked thanks

Answer
Your female is telling your male, that she is getting ready. She will may mount him to try and excite him, but she when she stands for him and flags him, she's ready.  Because she at day 3, it's too early.  

The most common reason a female doesn't take is because the mating has happened to early, or to late to catch her eggs. The best way to know for certain is to do simple progesterone testing.

An inexperienced male may or may not know it's time and may need help. Animals breed for procreation not recreation so he will get the hang of things.  But if he was in a confined upbringing without other dogs he may be to submissive to mount.