I concur with the Honerable gentlemen above, but I certainly wouldn't make it out to be so easy.
Where are you? what nation are you with. If for example your with the sarranids (with sarranid troops) against the Rhodoks then don't bother, just run away, those devilish crossbows with turn your men into pincushions instantly (A lesson I learnt very recently, 400 sarranids vs 140 arbelest wielding mothers. Never again.)
Seriously though, not everyone will be able, or in a position to crank out Huscarls and Sharpshooters quickly, if at all, so it really does depend on what troops you have in your army.
Your best bet here would be to convince another lord to join in with you, or join the marshals army when applicable. The more you fight in the large battles and sieges the more renown you'll get, and if you can take out a few lords on the battlefield on your own, all the better, more glory for you. The more renown, the more men you can have in your army, and the more likely it is your faction leader will give you a castle/city. Also, a handy tip, is look for castles/citys that have recently been taken FROM your faction, they will have a very small garrisons made up of mostly low tier units. Managed to take back Ukxhal from the Rhodoks with 60 mostly tier 3/4/'s in this manner.
Finally, If your not already, put every spare point into trainer, both on you and all of your companions, they all stack, honestly, every spare point that isn't being used elsewhere, being able to raise high level troops quickly is vital mid to late game, when you are going to be doing everything and your going to need to be everywhere because your nation is feasting (looking at you Harlous) and your the only one turning aside invasions.
If you give some more of the details we can be more specific.