In order to mark something as ‘except (A)’, or ‘besides (A)’,
以外（いがい） will be used. This construction is a combination of the kanji 以（い） which means ‘by means of’, and 外（がい） ‘outside’. This expression can most accurately be translated as ‘with the exception of (A)’, or ‘everything outside of (A)’.
To use
以外（いがい）, attach it to the thing that you want to highlight as being the ‘all inclusive’ amount/area.
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今日（きょう）は和食（わしょく）いがいのものが食（た）べたい。
Today I want to eat something other than Japanese food.
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タロウはゲームいがいに趣味（しゅみ）はあるの？
Taro, do you have any other interests besides gaming?
以外（いがい） is also regularly used simply as an expression of surprise, when someone sees, hears, or reads something that is ‘outside’ of what they expected. However, in these cases, the more correct kanji construction is 意外（いがい） ‘out of mind’. This is a regular mistake that even native speakers make, so in many cases, either 意外（いがい） or
以外（いがい） would be understandable.
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たかし君（くん）もアニメ好（す）きなの？ちょっといがいだね。
Takashi-kun, do you like anime too? I'm a little surprised.
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俺（おれ）こう見（み）えても意外（いがい）に肉（にく）を食（た）べないの。
It may come off as a surprise based on how I look, but I don't eat meat.