There are a few ways to improve the simple 'level stakes plan' (above), though it may make staking a bit more complicated, it can improve profits.
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A simple method is to increase the stake when the bank increases to a certain point (be it after the bank doubles, or after certain increases in cash ammount i,e, every £100).
For example, a £100 starting bank (5%-£5 stakes) has now doubled to £200 - you would re-calculate, 5% of £200 - so your next stake would be £10. and again when the £200 bank doubles to £400 - another increase would be due.
however this plan i wouldn't reccomend, as the increases in stake can be a little too much.
A safer staking stratergy would be to reduce the % when increasing stakes:
Example: same as above, but instead of re-calculating when the bank doubles using the same % stake as you started with you could reduce it by 1% - so would now re-calculate 4% of £200, and again when the bank doubles again, you would use 3%.
Another variation would be to wait untill the bank increases 200% before increasing the stake 100%.
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Adding an extra percentage of cash to the 'level stakes' is also a viable way of increasing profit. To do this you would use your normal level stake and add onto that stake an extra ammount, to work out how much extra to add - decide on a percentage of the profit that you should add on (usually in the 1-3% range). you would then work out how much profit your selections are in, then work out the percentage of that profit to add to the origional level stakes.
Example: your £5 level stakes bank of £100 has now reached £200. you decide to add on an extra 3% of the profit's to your origional £5 stake. so you work out that the bank is £100 in profit - so 3% of this is £3, which you will add to the £5 stakes, to create a new stake of £8.
This plan is quite good as it will increase stakes (potential extra profit) when the bank is in profit. but if the bank has losses then nothing extra will be added to the stake, as there is no profit to take a percentage from.