Try ensuring he's learning them in the order most schools follow:
1, 2, 5 and 10 are taught first (usually Y1/2 - and often by counting in 2s, 5s and 10s).
At some point you need to introduce anything x 0 = 0.
Then the concept of doubling is introduced. Once that's understood you can introduce x4 and x8 (x 4 = double and double again and x 8 = double; double again; and double again).
x3 (either by counting by 3s or learning them - many of which you'll already know from x1, x2, x4, x5, x8 and x10).
Once you know x3, then x6 is simply doubling x3.
x9 is all about patterns.
0 x 9 = 0
1 x 9 = 09
2 x 9 = 18
3 x 9 = 27
4 x 9 = 36
5 x 9 = 45
6 x 9 = 54
7 x 9 = 63
8 x 9 = 72
9 x 9 = 81
10 x 9 = 90
11 x 9 = 99
12 x 9 = 108
Several things here: up to x10 - the answer for 1x 9 to 10 x9 always starts with the first number one less than what you're multiplying 9 by - so 8 x 9 will start with 7. Then knowing that the digits in the answer always add to 9 means that you just have to work out what + 7 = 9. That's 2 - so 8 x 9 = 72.
Hand method - works to x10. Turn hands palm upwards with both pinkies together. Numbering starts at left thumb = 1, left index finger = 2, etc... to right thumb equal to 10. Fold over the finger that represents what you're multiplying 9 by - so let's say it's 3 - (folding over left middle finger) you'll have two fingers up to left of folded finger which represents tens and 7 fingers up to right of folded finger - that's units. So 3 x 7 = 27. Just remembr fingers to left are tens and fingers to right of folded finger are units.
That leaves 7. Which by now isn't so awful because you already know 7 x 0, x1, x2, x3, x4, x5, x6, x8, x9, x10 - so just need to learn 7 x7 = 49.
11s are fun because it's just double digits to x9 (i.e. 2 x 11 = 22). 10 and over there is a trick to 11s. Whatever number you're multiplying 11 by can be treated as follows: 14 x 11 (first digit / first + 2nd digit (may need to carry to hundreds place) / 2nd digit) - so with 14 x 11 = 1 / 4 + 1/ 4 = 154. With larger numbers that involve carrying over so say 29 x 11 = 2 / 2 + 9/ 9 = 2 / 11/ 9 but have to carry over 10 tens to hundreds so 2+1/ 1/ 9 or 319.
That leaves 12. Well we've learned everything except 12 x 12 which is 144. Memorise that and you've learned them all! Hurrah!
We've found learning by playing video games has slipped in practice without the DCs realising it. Practice ideas here:
As someone suggested Timez Attack: www.bigbrainz.com/. The free version has been fine for us. Tests your child and starts at where they're at.
Multiplication dot com: www.multiplication.com/
Maths Champs (7 - 9 games have lots of multiplication/ multiples games): www.mathschamps.co.uk/games7-9
Woodlands Junior school Times tables games: resources.woodlands-junior.kent.sch.uk/maths/timestable/index.html
Ambleside Primary table trees: www.amblesideprimary.com/ambleweb/mentalmaths/tabletrees.html (gentle practice of individual tables (great for more practice with that table that just defies learning).
Mumsnet has an interactive times table activity that mixes them up in grids: www.mumsnet.com/learning/maths/interactive-times-tables-activity
HTH