I must say that I like Sardegna a lot, I think it is WRC event where I was the most times (once it was IRC). So I can highly recommend it - nice gravel stages, usually nice weather, I dont remember any problems with marshalls. Regarding the recommendations - if you have ever watched any rally as spectator, you can use same preparation like for other events - mainly you can look at the maps and compare it with the last year, then watch onboards and find the best suitable place (and if there is lot of spectators on the video it meens it will be good accessible spot). Then you can watch also official programme of the rally, where should be also some tips for spectators, who are not able/have no time to do better preparation before the rally. Or you can ask fans here to recommend some specific places to watch (you should write what type of places you prefer).