FFF, you use whatever tools are available. If radar advisory services are available you'd use them. If RIS then take advantage of that, if no radar then use whatever information service(s) are available. If no information services then listen out & make broadcasts at marked position reporting points. If no marked reporting points then at regular intervals or on hearing a potential conflict.
If you have the benefit of TCAS then that is a great aid no matter how many or how few FS/ATC services are available.
No matter what equipment or services are there, keep looking for traffic as weather permits.
Make use of defined procedures eg quadrantal/hemispherical levels, published tracking requirements such as northbound traffic to track via ABC, southbound via XYZ.
Plan your route to avoid departure & approach procedures if possible.