Across the floorboards is the accepted way to do it but I do wonder about access to cabling, pipes etc. that my run under your floor?
If you lay it in line with the floor boards, then you could ensure that the joins in the laminate sit midway (ish) between the joints in the original boards - thus allowing easy access to said pipes, cables etc.
Having said all that, it would be a nightmare lifting the laminate anyway :?
Depending on the underlay, I dont think it really matters. If you have the green fibreboard stuff rather than the thin sheet material it should support the laminate along rather than across the original floorboards fine unless they are really uneven.
The only reason to lay across existing boards is to stop the laminate join and floorboard join lining up and providing a weak spot when pressure is applied to the floor. A good underlay spreads the load and should prevent this. I usually lay to match the room size rather than the floor boards ie to prevent the room looking long and narrow etc.
Locking laminate rather than glue laminate is easy to take up and relay, so long as you dont put skirting on the wall to cover the edge of the laminate (DAMHIKT )
when I layed a locking wood laminate (Kahrs, I think) I replaced the skirting boards at the same time. The new skirting is layed over the flooring and screwed to the walls. The screw holes are filled with tapered plugs and NOT glued in so I can whip of the skirting quite easily.
In fours years the unglued plugs have shown no sign of movement.
The usual recommendation is to lay at right angles to whats underneath. Another consideration is natural light source ie the window. the floorboards look better if laid at 90 deg. rather than parallel to the window, that way the join between boards isn't so obvious.
i agree with you all two main factors ,thickness of underlay and acess to water pipes ,we all know leaks develope from nothing, i think the best route is to sand the exsisting boards, any bad boards can replaced , take a sample piece to your local reclamation yard, i am sure it will save money in the long run, and the finished result is far more pleasing
i agree with comments above,but check out your existing floor for creaky boards ,loose nails etc before starting the job.Isometimes lay the underlay across the boards, and the lami with the boards but this depends on the room size and of course window position as Manny points out,good luck.