Personally I only really know if I really like a wine when I've had about half a glass of it. The first sip unfortunately always tends to taste the best to me and then the rest of the glass is like an adventure, discovering wether or not a wine holds up being drunken over an extended period of time compared to when it first hit my palet. This is also different from the aftertastes one gets after having taken a sip and swallowed in the seconds or minutes after that if you don't take another sip and don't eat anything and there are no strong smells surrounding you. This is more of a... okay so the first sip of a wine hits my palette most times (unless it is a really refined, complex and layered wine) the most with all the facets and qualities of its bouquet all at once so therefor that sip tends to taste well-balanced in general to me. But then after I drink the same wine for a bit longer most aromas and flavours start to drop to the background or even into obscurity with just a few of them and its qualities or even just one flavour overpowering the more subtle flavours and aromas that were still present in the beginning... and then its the question wether or not I still like the wine like that.

Hi Dalia, MyWineSmarts gave a great explanation about white wine basics here! If you're interested in learning even more, check out my 21 Days to Wine KZfaq series! Episode 1 begins with an Intro to Wine Tasting. Let me know what you think!