i am using one common methods for AFNetworking WS Calling.
Uses:

Call WS:

NSDictionary* param = @{
                        @"action":@"helloWorld",
                        @"query":@"{\"name\":\"john\"}"
                        };

[self requestWithUrlString:@"URL" parmeters:paramDictionary success:^(NSDictionary *response) {
    //code For Success
} failure:^(NSError *error) {
   // code for WS Responce failure
}];

Add Two Methods:
this two methods are common, you can use these common method in whole project using NSObject class.
also add
// define error code like…

define kDefaultErrorCode 12345

- (void)requestWithUrlString:(NSString *)stUrl parmeters:(NSDictionary *)parameters success:(void (^)(NSDictionary *response))success failure:(void (^)(NSError *error))failure {

[self requestWithUrl:stUrl parmeters:parameters success:^(NSDictionary *response) {
    if([[response objectForKey:@"success"] boolValue]) {
        if(success) {
            success(response);
            
        }
    }
    else {
        NSError *error = [NSError errorWithDomain:@"Error" code:kDefaultErrorCode userInfo:@{NSLocalizedDescriptionKey:[response objectForKey:@"message"]}];
        if(failure) {
            failure(error);
        }
    }
} failure:^(NSError *error) {
    if(failure) {
        failure(error);
    }
}];}

and
// Set Headers in Below Method (if required otherwise remove)

- (void)requestWithUrl:(NSString *)stUrl parmeters:(NSDictionary *)parameters success:(void (^)(NSDictionary *response))success failure:(void (^)(NSError *))failure {

AFHTTPRequestOperationManager *manager = [AFHTTPRequestOperationManager manager];
[manager setResponseSerializer:[AFHTTPResponseSerializer serializer]];


[manager.requestSerializer setValue:@"WWSE profile=\"UsernameToken\"" forHTTPHeaderField:@"Authorization"];



[manager GET:stUrl parameters:parameters success:^(AFHTTPRequestOperation *operation, id responseObject) {
    if([responseObject isKindOfClass:[NSDictionary class]]) {
        if(success) {
            success(responseObject);
        }
    }
    else {
        NSDictionary *response = [NSJSONSerialization JSONObjectWithData:responseObject options:NSJSONReadingAllowFragments error:nil];
        if(success) {
            success(response);
        }
    }
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
    NSLog(@"Error: %@", error);
    if(failure) {
        failure(error);
    }
}];}

For any issues and more Detail please visit AFNetworking

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UPDATE
———- migrating with AFNetworking 3.0 ———
migrate your AFN-2.0 to 3.0 with Some small changes please chaeck here AFN 3.0