Look for groups of five
The 5 times table grows in steps of five. Six groups of five make 30, so 5 × 6 = 30. As the number of groups increases, the totals alternate between ending in 5 and ending in 0. That pattern can help you check an answer.
Connect fives and tens
Ten groups of six make 60. Five groups are half as many equal groups, so half of 60 is 30. This gives another way to understand 5 × 6 = 30 when a fact does not come to mind straight away.
Use the pattern, then practise recall
The ending pattern is a useful check, but it does not tell you the whole answer by itself. Use equal groups or the connection to ten to find the total, then practise until the facts become easier to recall.