Employment and freelance contracts are usually signed without reading. A small number of clauses determine what happens in every situation that matters.
Notice periods
How much notice each side must give. Frequently asymmetric, and a long notice period from you with a short one from them is worth negotiating.
Check whether it changes during a probation period.
Intellectual property
Who owns what you create. Standard for work done for the employer. Watch for clauses claiming ownership of anything you create during the employment, including personal projects in your own time.
That is common, frequently unenforceable, and worth amending anyway.
Restrictive covenants
Clauses preventing you working for competitors or approaching clients after leaving. Enforceability varies enormously by jurisdiction and they can create real difficulty regardless.
Check the duration and how broadly competitor is defined.
For freelance specifically
Payment terms – when you get paid after invoicing, and what happens if they are late.
Scope, and what happens when it changes. A contract without a change process means every addition is unpaid.
Termination, including whether you are paid for work done if the project stops.
And liability, particularly any clause making you responsible for consequential losses, which can be unlimited.
The practical approach
Read the clauses about ending the relationship, ownership, and money. Those are where the disputes come from.
Asking for a change is normal and rarely costs you the role. The worst outcome is usually that they say no.
The caveat
General guidance. For anything substantial, a lawyer who knows your jurisdiction is worth the fee.