In general, you can't!
In a few particular cases - which are unlikely in seeds from commercially grown fruit - it is possible. For instance, if the pollen parent is trifoliate, then trifoliate seedlings are the result of fertilisation. Similarly, with other varieties that have markedly different leaf characteristics.
However, seedlings from some citrus varieties are virtually always clones as the fertilised embryo does not develop. In others, if you sow a lot of seeds in identical conditions you will find most are very similar and some are obviously slightly different. The similar ones are likely to be clones. Other citrus, such as pummelos, always produce variable fertilised seedlings.
There are lists and research papers around on the internet which rank citrus species and varieties according to these characteristics.
You will need to do some Googling on citrus polyembriony and zygotic seedlings etc.
Alternatively, just sow the seeds and enjoy the results! You are quite likely to get a clone or something very similar to the parent.

Citrange,
Thanks for suggesting search terms. From that I learned about nucllar embryony, which I what I want to obtain from seed: Seedlings that are formed from the seed tissue without genetic qualities from the pollen provider.

According to some webpages, it is common in some citrus varieties, such as rough lemon and sour orange, while rare in others. It seems the first shoots are the ones most likely to be unfertilized, and the later shoots zygotic.

From the webpage linked below, quoting Tom McClendon in 'Hardy Citrus for the South East':

"Most common citrus such as oranges, grapefruit, lemons and most mandarins are polyembryonic and will come true to type. .... The good news is that polyembryony helps stabilize varieties, which allows seeds to be passed around with little chance of spreading diseases such as viruses. This unique characteristic allows amateurs to grow citrus from seed, something you can't do with, say, apples."

Now I am optimistic!

John

Here is a link that might be useful: Citrus Pages - Nucellar Embryony