well, i use a two stage process. 1 step - raw approximation, 2 step - fine estimation :)
you gotta estimate your load. cargo + passengers.  
Then you gotta estimate your cruise fuel using your tables. Say you need to fly 900 nm. your estimated groundspeed 450 knots, so 2 hours of cruise.
select cruise altitude. estimate fuel quantity for 2 hr cruise, add descend and land fuel + reserve. so you have weight without TO and CLIMB fuel.
So you will be able to estimate TOGW using TO fuel table. Add TO and climbout fuel from table.
using estimated TOGW and recalculate cruise FLIGHT LEVEL and cruise fuel for your TOGW. You'll get another cruise altitude and fuel, so you can recalculate TO fuel and get your more precise TOGW.

2 iterations enough for good calculation.

If you have wind aloft data, then after first estimation of TOGW, you can add wind correction to speed, and that will give you another trip time and another cruise fuel. Dont forget to put some reserve and descend\ land fuel.

Give me your route (its VOR to VOR i guess), i'll give you calculations as example. i logged more flight time in 703 then in 727 mostly because of longer routes for 707, so more flight time. I arriving to destination under Max Landing weight, but with required reserves.