Well, since no-one else has chipped in, I throw my two bits in the pot.
Plan your OG and FG well. Pay attention to your yeast's attenuation and what that means for your FG. If you have a yeast that only attenuates 68% and your OG is 1.095, your going to likely end up with a really sweet beer that might end up cloyingly sweet (FG around 1.030, which is pretty sickly sweet). Ive done two barleywines and both ended between 1.020 and 1.025 and both were great.
Remember that as you increase your grain bill you may end up having to thicken your mash depending on the size of your equipment. The hypothetical 1.095 OG beer making a 15gal batch would need about 50 lbs of malt (using avg ppg of 37 and 75% total system efficiency), which takes up about 10 gal all by itself plus almost 17gal of strike water to get a 1.3qt/lb ratio in the mash. Even a 1 bbl keggle mash tun is going to be near brimming with 27 gal of mash in it. Before you dump $60+ worth of grain in your tun, do a test to make sure that volume of liquid and grain wont be a problem.
In general, it seems to be better to scale down how much beer you expect at the end rather than thickening your mash and taking an efficiency hit. Once you start thickening your mash (and reducing your efficiency!), each lb of grain you add increases your OG less and less. The other option is to use some extract to boost your OG at the start of the boil after mashing.
Fermentation will start slower and take a little longer as the yeast have their work cut out for them. It will also take longer for the beer to carb up if bottle conditioning as that is the last sugar the yeast gets to ferment and it will be tuckered out by then. Definitely use yeast nutrient and aerate the crap out of the wort before pitching. The yeast will be under a lot of stress with the higher alcohol content and will need the boost.
While mashing, consider doing a multi-step rest mash with a lower temp hold (140-145) to increase the fermentability of your wort. The reason this works is that beta-amylase and limit dextrinase both work in that temp range but are denatured at normal mash temps (154-158). These help break down longer sugars and the branch points in the starch chain that the alpha-amylase (which works in that higher temp range) cant. Ive found that I can get 3-5% more attenuation than normal if I do a 30 min hold in that 140-145 range before finishing my mash (nother 30-45 min) at 155-156. This can help if you really want to use a type of yeast that normally has a lower attenuation, but still want a strong beer. The trade off here is that you loose some body in the beer. You can account for this by being a little richer in body-building grains (i.e. cara/crystal malts, munich, aromatic, etc), adding extract after the mash, or even adding a bit of lactose (which the yeast cant break down).
Final though, use the most important tool in the brewer's tool box, patience! Big beers take a long time to condition properly. My last barleywine was brewed in August. It took a full month to carb, but wasnt really conditioned until 2 months in. Now, 3 months later its really getting good. If I stretch out the last case for another 2 months, I get the feeling I will be declaring "best beer yet" when I pop one open.
