In reply to JonC:
Loads of good advice on here, showing a range of different approaches. Some random additional/repeat observations (and they are not necessarily the right way or only way, just the way that works for me):
If your goal is to be an all rounder solid at the grade, choose a route that plays to your weaknesses. But if you want to get the tick, choose a route that suits your style.
When you get on a project and it feels wrong, just walk away and find another. If you get on a project and it feels as though it suits you but it just feels too hard, stick at it and you will be amazed at how something can go from feeling beyond you to do-able.
Climb with loads of different people to learn from them and find partners of a like mind for what you are trying to do with that particular project. If you both really like each other and get on and have similar goals, it is a fundamentally better experience and you will climb better too.
Do falling practice and keep doing it, and it needs to be specific to the particular clips and to the particular climbing partner.
Don’t be afraid to get on your project in bad conditions because when you get on it in good conditions it will feel so much easier,
Talk to each other: verbalise the moves and describe holds in a really specific way. That will help you both memorise them. Write the move by move beta down when you get home so you don’t forget. It also (a) helps you visualise and (b) realise which bits you are still unsure about.
If you are going to get trashed bolt to bolt climbing to get the clips in, I don’t see the point in that: use a clipstick. Furthermore, trashing yourself getting the clips in will make the route seem way harder than it is. Same for going for the on sight if the route is an unrealistic proposition to on sight.
Warming up on easier routes is often a mistake as you can get flash pumped trying not to fall off it. I prefer to warm up on my project clipsticking up it and re-familiarising myself with the moves but being sure not to try to perform, sitting on a bolt/the rope as soon as I feel myself starting to strain.
When working the route on top rope, after doing a few moves and resting, remember to place your hands and feet on exactly the same holds before climbing again if they were the right ones. That way you don’t get skip moves or head off on a different sequence.
Actively look for every rest and half rest that you can. You will be amazed where you can get hands free or almost so. Toe hooks are great for taking a bit of your weight, same for thumbs, elbows, forearms, sneaky knee bars, heel hooks, bum, head, anything.
Work out whether it is your left or right arm that’s going to get pumped first and then clip, rest/semi-rest and choose a sequence that leaves it most rested for when you need it most.
Don’t wait until you can do the route on top rope before getting on the lead, as the lead is a different experience with the clips, potential falls and so on, and it will feel like you have done it on top rope and so somehow you *should* be able to lead it: it’s all likely to be less fun this way and feels retrogressive. In contrast, more or less working it out on top rope or bolt to bolt and then going for the redpoint is more likely to feel positive.
Buy some belay glasses and share them with your mate! Fantastic bit of kit. Aside from saving your neck, you can both be more attentive belayers with ease and get help with beta a lot more.
When working the route on top rope especially if it is a long route, rest by clipping a daisy chain from your belay loop to the upper krab of the quickdraw. That way you can unclip the rope from the draw easily before pressing on (instead of getting pumped senseless merely trying to unclip). Also, you won’t sag down the route on rope stretch. Also, it’s a lot more considerate to your belayer who doesn’t have to take in loads of stretchy rope or hold you on the rope while you rest: that said, it is often better to rest on the rope and that is something you both do for each other as belayer. Word of caution: do not be tempted to climb up at all while clipped in with your daisy: it has zero stretch and falling from even just 18 inches above the bolt can result in you slamming into the rock dangerously hard.
If one of you is still working the route and the other is going for the redpoint (perhaps more than one attempt), the latter has priority in terms of calling the changeover. It can be frustrating if you are ready to try to redpoint and your mate takes that bit too long and you cool down too much.
Even when you think you have the beta totally sorted, be open to the possibility that it can be refined.
When on the redpoint and you mess up a section, don't give up because there is every chance that you will somehow or other sketch your way to the top.
Get the last so-called easy/easier bit dialled so you don't fall off it.
When stripping the route, if there is an awkward QD lower down, tram to it and take the lower one out before the easier higher one.