I'd say the key things to look for are the physical 'bones' of the wood- location, drainage, access, size, incline, boundaries, public access. - and price
I'll explain briefly a summary of the other 4 woods I put bids in for, the price they went for, and why I'd have paid even more than the top end price we paid to secure ours. They are useful 'case studies' to show what to look at.
Wood 1) 14 acres, 1 mile from home. Mixed conifer and deciduous, well drained, good access, flat, reasonable boundaries, no Public access. Cons- not far from encroaching suburbs, commercial conifers on large part so lacked character, some road noise. Bid £70k to Cleggs, but wealthy investor put in £250k bid for all three of the vendors woods shutting us out.
Wood 2) 3.5 acres on a hill top 10 miles from home. Ancient deciduous, well drained. degree of slope, awesome views. Lots of character. Problem- No Access, narrow lane with steep sides meant it was only a walk-in wood. After initial £22k bid, we withdrew due to the unresolved access problem. Eventually sold to London buyer for £42k who wanted a source of green oak. Interesting, as there wasn't a single oak tree on it.
Wood 3) 3.5 acres 'Arboretum' feel with some specimen very old yews and chestnuts. Level, drive straight in, secluded. 25 miles from home. Offered £50k but it went to auction and sold for £68k. Cons; too far, too expensive.
Wood 4) 2.5 acres. Incredible location. Hidden in a 'secret valley' 16 miles from home with a to-die-for small river with waterfalls as one boundary, and a Mill leat as the other, caravan parked in it, very narrow and long. In effect a River bank recently planted. Bid £25k but withdrew when it was getting silly, and it was really a River bank, not a wood. Sold for £42k after final bids invited.
Wood 5) Ours; 5.3 Acres, 3 Miles from home. Ancient with 150 magnificent Oaks up to 400 yrs old. Quiet location served by a lane. Well drained. Excellent drive in access off road with 1/3 acre hard standing. Surrounding ditches, woodbanks and hedges make it feel like a private walled garden. Every visitor says its the prettiest wood they've ever been in. No public access. Perfect. Visited every day for a month before auction, fell in love and had decided it was ours. Held hand up at (hotly contested) auction until we got it and would have paid more. That was the first time the wood had been sold as an individual plot in the last 1300 years, previously part of large 2000 acre estate. Now realise with the timber value the £72k was actually a bargain, would never sell. Visit every day. Bliss.