Many words in a foreign language will be similar to words in a language you already know. Sure, some of these will be 'false friends', such as French 'éventuellement' (meaning 'maybe') and English 'eventually' who look very similar but have different meanings. But most cognates - words that look similar in two different languages - are real friends. That means that to remember them all you need is see the similarity with the other word you already know. You will do this without having to think for most words (French 'le restaurant' is English 'the restaurant'). Other similarities will come to some people earlier than others (cat/chat, to flirt/compter fleurette, etc...).

With some basic etymological knowledge, but you can also investigate a little closer words that at first do not seem to be similar in any way, but are. For instance, French and English have many shared words who only differ by one letter. Where French uses 'G', English puts a 'W'. To learn that French for 'warren' is 'garenne', all you need is replace the 'g' by a 'w'. The same goes for William/Guillaume, war/guerre, warranty/guarantie, ward/guarde, wasp/guêpe, wage/gage, etc...

The more you study languages, the more attractive it will be to notice these hidden similarities and to use them to recall new foreign language words.