Intrusion law in Texas does not differ substantially from the law described in the General Elements of an Intrusion Claim section of this guide. See Billings v. Atkinson, 489 S.W.2d 858, 859 (Tex. 1973). As result, you should follow the general advice outlined in the section on Practical Tips for Avoiding Liability When Gathering Private Information.
Texas courts also require that the intrusive acts "be about or directed at" the plaintiff. See Doe v. Mobile Video Tapes, 43 S.W.3d 40, 49 (Tex. App. 2001). It is unlikely that this requirement has any practical impact on what is necessary to prove intrusion.
You should also be aware that repeated, harassing telephone calls may give rise to an intrusion claim in Texas. See Donnel v. Lara, 703 S.W.2d 257 (Tex. App. 1985).