In an earlier post, I noted that there are some benefits of providing an initial claim with concrete structure and limitations so that someone reading the claim can instantly understand the invention and its benefits. This helps frame the invention in the minds of the reader and may be especially important when the USPTO Examiner flips to Claim 1 before reading anything else in the patent application.
There are, however, limitations to this approach. In particular, 37 C.F.R. 1.75(g) provides that "[t]he least restrictive claim should be presented as claim number 1." That rule of practice was added in 1996 along with other changes for implementing the 18-month publication rules. The purpose of the change was "to facilitate the selection of a representative claim" to be published in the Gazette.
Although the rule is in place, it appears to be rarely -- if ever -- enforced. The Manual of Patent Examination Practice (MPEP) interprets the rule as a should rule rather than a must rule.
Claims should preferably be arranged in order of scope so that the first claim presented is the least restrictive. MPEP 608.01(m)
Further, a search of CAFC, District Court, and BPAI opinions along with law review articles reveals only two passing mentions of the rule. (Interestingly, the law review article appears to incorrectly interpret the rule).
Of course, the fact that the rule has not been enforced does not lead to the conclusion that the rule will not be enforced against your client. (I.e., down the line it might come up once again).
The right aproach: Of the usual three independent claims, it is often difficult to determine which is the least restrictive because each may approach the invention from a different perspective. If one is clearly the least restrictive then it should be listed as claim 1. If some ambiguity remains, choose the claim that is the most concrete, fleshed-out, and understandable and list it as claim 1.