As a side note, if playing as ENG/Britain, if you're going to build special forces, be sure to do the NF and get David Stirling - that +20 per cent attack is not to be sniffed at, and can make a good special forces template very handy.
More broadly, keep in mind that special forces are significantly better with the full tech investment (and moreso if you go with the top than the bottom path) - with bonuses to attack, org and climate acclimatization (so better in hot and cold environments, as they'll acclimatise better).
Other tips are to set the template to "elite", so it gets the best kit (this isn't anything special for special forces, but if you're going to use them as an elite force, then this helps them double-down on this) and being careful not to add too many non-special force frontline battalions, as that'll dilute the terrain bonuses. I usually use support ART and AT (with AA if playing as someone unlikely to have decent air support), and then logistics (good for Marines and Paras) and field hospital (good for reducing experience loss from casualties, as well as the net manpower impact from casualties) - but I tend to go with more support battalions than may be optimal from a min-max angle (I wouldn't know, I'm not a great min-maxxer).
As others have well said, the default special forces templates are fairly small forces, so won't have much luck against a full-sized division - so if you want to use them as normal divisions, be sure to bulk that template up.