What are people's thoughts about the best strategies for the Inner Sphere to use against Clan forces (that is, Clan tech and Clan-level skill of pilots)?
In particular:
(1) It seems to me like the light weight class of IS units is pretty doomed against the Clans, due to the ease of hitting fast-moving units with Clan pulse lasers. So if an IS player wants fast units, they should probably choose fast mediums or heavies rather than light units that rely mainly on speed for defense. Does that sound right?
(2) Should you take as many long-range weapons as possible? Or give up on the long-range game and just try to close in to short range and fight the battle there?
(3) What about if you're trying to take on the Clans with 3025 tech?
(4) Just in general: what works against the Clans given their many advantages?
(Obviously this is intended for those eras when the IS has no access to Clan tech)
My thoughts from a purely game mechanical point of view:
1) You can use lights, but don´t overdo it. Your lights should mount pulse lasers and have good armor.
Check the armor on your lights. A single Gauss or cER-PPC hit (or 2 hits from a medium pulse laser) shouldn´t be enough to take off a leg or a side torso.
If you select IS units restricted by faction than sometimes you wont have a good light mech pick. In that case you have to rely on mediums to fill that role.
You can also take light vehicles instead of light mechs. The Minion, the Lightning are fast and accurate. For longer range firepower the Main Gauche, or Scorpion (LRM) are decent an cheap tanks.
2) I rarely would skip long range weapons entirely, clan opponent or not. It´s entirely possible to end up having more raw long range firepower than your clan opponent if you focus on that aspect. In my experience it is uncomfortable for clanners if you can field multiple long range weapons per mech and (somewhat) keep up in movement speed.
For example for heavies you can use depending on the era:
Grand dragon-5K, Maelstrom, Ninja-To, Argus-2d, Rakshasa-1A, Hercules, etc.
Or you can go the 4/6 speed wall of steel route (FWL is quite good for this):
Orion, Perseus, Apollo, Warhammer, Blackjack Omni-E, Avatar-O, -B, -C, etc.
BV-wise, you want to have the most bang for you buck. Mechs like the Falconer are not good value in a BV game, even if the fluff depicts is as a nemesis against clan. In that price range you could field a Warhammer-9d. I is just as fast, sturdier and more accurate.
For close range combat focus on speed, armor and (pulse) firepower. Premier examples are the Wraith an the Lightray-4W. They can hunt down clan lights and mediums, backstab or charge heavier and slower units. Good heavy examples are the Black Hawk KU, Rakshasa-2A, Ti Tsang, etc.
3) Same principles apply but w/o pulse lasers.
4) As others have allready mentioned terrain and map size are important.
In general, flat featureless terrain that isnt to big tends to favour the IS. You need fewer turns to get into closer range and there is nowhere to camp/hide for your opponent. The more terrain there is the more a clanner is able to leverage the firepower, or more abstractly the BV imbalance, by exposing himself to only one IS unit, while obstructing LoS to all others.
Map Size is something you have to negotiate with your opponent. I´d comfortably play with a trinary of clan mechs vs an IS opponent and equal BV on a 3x3 map (roughtly 50 x 50 in megamek). Plenty of room to move, flank, backstab and camp IMHO. Other clan players might disagree and mumble something about phone booths.