Fruits are produced on one year old stems, so after fruiting, remove the older canes and train-in this year's growth to produce fruiting canes for next year.
If there is not enough new canes to produce a decent sized plant for next year, leave some of the older canes in and prune their sideshoots back to an inch.
By training the plants over wires or fencing you are maximising exposure to sunlight needed for ripe fruit and by supporting the stems away from the soil, keeping them from rooting into the ground and spreading uncontrollably. Remember to try and keep new and old canes separate as they grow to make further pruning and training easier
RJB