When I first learned numbers in Spanish I couldn't remember them at all. That was until my teacher pointed out the similarities between the lower numbers and the higher numbers - it clicked immediately and I haven't had trouble since. I decided to try and use the same strategy in teaching my own students English numbers and I created a simple worksheet that shows similar numbers enclosed with a border. In addition, there are exercises to complete in which they use the given numbers in the top section as a guide. I paired this with numbers bingo (another worksheet on here) and the lesson worked out really well.