Actually, there are no standard rules regarding forex pairs for beginners. The selection of this pair depends on the strategy and characteristics of each trader himself. Therefore, choosing a suitable forex pair for beginners must be based on personal observations.
The recommended forex pairs for beginners that are usually given are EUR/USD and USD/JPY for major pairs, and EUR/GBP for Cross pairs. These pairs tend to be easier to analyze, because they can show a more predictable trend, and their characteristics do not hold too many surprises.