Regarding whether you should ask people about the pronunciation of their names, pretty much yes. With only the kanji, it could actually be very hard to read names correctly. Many names have multiple readings. For example, the surname 高城 could be pronounced either as たかじょう or たかぎ. The name 陽菜 could be pronounced either as はるな or ひな. The common female name 玲奈 could be pronounced as either れな or れいな, and outrightly mispronouncing one's name could offend some. Of course, if the person's surname is rather regular, such as 高橋｛たかはし｝ or 田中｛たなか｝, there is usually no need to ask. But, in general, only the person him/herself knows the pronunciation of their name for sure and others should always follow him/her i.e., even if someone is named 一二三 and want you to read his name as ドレミ, トランプ or even バカ (although I don't know why one would do so), you should call him so.
人名用漢字｛じんめいようかんじ｝ refers to kanji that could be used in names which are not jōyō-kanji. 常用漢字｛じょうようかんじ｝ are also valid kanji for names: otherwise, simple & common kanji characters such as 花 and 子 would not be valid in names, which is absurd. The Japanese Wikipedia page on 人名用漢字 is a rather good place to learn more about 人名用漢字.
In fact, however, 人名用漢字 consists of many quite common kanji that aren't part of 常用漢字 for some reason. One example would be the character 遥, which is very common in female names, but also in the word 遥｛はる｝か "distant". Also, many of the 人名用漢字 are simply variants of common jōyō-kanji. For example, the unsimplified form of 桜, i.e. 櫻, is part of 人名用漢字 (partly because the character 桜 is considered misfortunate for names due to its number of strokes). 嶋, a variant of 島, is seen in surnames.
However, note that sometimes kanji that are neither 常用 nor 人名用 CAN appear in surnames. For example, the common surname Watanabe 渡辺 has two old-fashioned variants, 渡邉 and 渡邊, which are still common. However, neither 邉 nor 邊 is in 人名用漢字.
The answer is, NO. Many 人名用漢字 are actually rather rare even in names, and people generally don't know how to read them. However, even if the characters are rather common, they might have special readings in names. For example, the surnames 五十嵐｛いがらし｝ and 我孫子｛あびこ｝ contain no rare characters, but their readings in these surnames are quite eccentric.
In Japanese TV drama, anime and manga, it is common to present characters' names with furigana when they first appear. So, no, it is very common to give furigana with names. When you register for accounts on Japanese websites (go to Amazon Japan and see!) or fill in forms such as customs declarations in Japan, there will always be a space for フリガナ of your name. Thus, it is never strange, and kind of actually mandatory, to provide furigana for names.