All the obvious things: encouragment, re-inforcement, bribery (ice cream anyone
), hand holding. Some children are cautious, which is a good survival trait
. Some children are dare-devils and throw themselves into (and off of) everything. It will probably improve with age.
With food things, put them on the plate every time and don't worry if they are left, veg and such can be chopped in a processor then hidden in mince or soups, so that the taste becomes familiar without scary shapes.
Encourage independant play with friends, they'll often follow friends where they wouldn't follow siblings.
Some things are worth pushing; some not. Pick your fights. If you want them to ride the bike for example, promise a trip to an ice cream shop or other favourite place when they've done it. If you want them to try a maths problem without disolving into tears because "I can't DO it", sit down with them and go through it calmly and encouragingly until they CAN do it, with lots of praise and a reward at the end.
Try to be as relaxed about it all as possible and good luck
.