Assuming you are using Polybian troops - I find the old checkerboard technique works quite effectively. You cant leave the Hastati to fight on their own for long mind, but nonetheless i do keep the gaps between the maniples. Just hold the Principes back long enough to chuck most of their javelins then charge in and its usually enough to win the centre. The flanks can usually be held by auxillaries / cavalry / skirmishers. Hold the triarii back until the enemy is exhausted and them commit them to the critical point of the battle. Fresh troops in reserve does work in EB.

The vital part IMO is making use of all your javelins, as it makes the brawl a lot easier to win, even on the harder difficulties.

Against phalanxes or large numbers of cavalry, then just like in real life tactics need to be adapted.